Players are graded on a 20-80 scale for future tools -- 20-30 is well below average, 40 is below average, 50 is average, 60 is above average and 70-80 is well above average.
Check out all 30 team Top 20 lists and the Top 100 on Prospect Watch.
1.Taijuan Walker, RHP
Preseason rank: 1
MLB Top 100 rank: 8 (Preseason: 6)
Scouting grades: Fastball: 70 | Curveball: 55 | Changeup: 55 | Control: 50 | Overall: 65
A year after being the youngest pitcher in the Southern League, Walker returned to Double-A Jackson to start 2013. Walker fared much better the second time around, pitching his way to Seattle in August for his Major League debut.
Walker came late to pitching after playing mostly shortstop and basketball in high school, and he is still developing from a thrower into a pitcher. That is especially apparent in his command, which he will need to tighten to reach his lofty potential. Walker gets easy velocity on his fastball, throwing it in the mid-to-upper 90s. Walker also throws a changeup, a curveball and a slider that often moves like a cutter. All of his offspeed pitches have the potential to be above-average offerings.
Walker's youth, athleticism, size and stuff all give him the chance to develop into a front-line Major League starter, though shoulder soreness in 2014 slowed his progress in that direction.
2. Alex Jackson, C/OF
Preseason rank: None (2014 Draft)
MLB Top 100 rank: 39 (Preseason: NA)
Scouting grades: Hit: 60 | Power: 60 | Run: 45 | Arm: 55 | Field: 45 | Overall: 60
The top high school bat in the 2014 Draft class, Jackson became the fifth first-round pick out of Rancho Bernardo (Calif.) High School in suburban San Diego in the past two decades when the Mariners took him with the sixth overall selection.
Jackson's standout tool is his right-handed power, which he generates with bat speed and strength. Jackson has enough feel for hitting that he could hit for average in the Major Leagues, though he'll have to be sure to curb a tendency for his swing to get long at times -- which causes him to miss hittable fastballs.
Jackson's arm gives him a third future plus tool. A catcher in high school who also played elsewhere, Jackson was drafted as an outfielder, meaning his days behind the plate were over. His arm and athleticism fit well in right field, and the move should allow Jackson's bat to move through the system faster.
3. D.J. Peterson, 3B/1B
Preseason rank: 2
MLB Top 100 rank: 55 (Preseason: 88)
Scouting grades: Hit: 60 | Power: 60 | Run: 40 | Arm: 60 | Field: 40 | Overall: 55
The Mariners drafted Peterson out of high school in the 33rd round in 2010, but he chose to attend New Mexico instead. It proved to be a fruitful decision, as Peterson established himself as one of the premium college hitters in the 2013 Draft class. The Mariners didn't miss a second chance at him, selecting Peterson 12th overall.
Peterson has a quick swing and an advanced approach at the plate. He showed off his impressive power as a professional, hitting 13 home runs in 55 games after signing.
Peterson played third base in college, but his future may be across the diamond. He has a good arm and moves better than his size would suggest, but his defense is adequate at best at third base. Peterson's bat will play anywhere, and it should help him move quickly toward Seattle.
4. James Paxton, LHP
Preseason rank: 3
Scouting grades: Fastball: 60 | Curveball: 55 | Changeup: 40 | Control: 45 | Overall: 55
Paxton has been an intriguing yet enigmatic lefty with electric stuff, since his pro debut in 2011. His brief big league debut in 2013 had some thinking he was ready to put it all together, though a lat strain forced him out of action for most of the first half of '14.
The former Futures Game participant has many things going for him, including two above-average or better pitchers in his fastball and curveball -- all coming downhill from a 6-foot-4 frame. Since Paxton can touch 95 mph from the left side to go along with that solid breaking ball, having a below-average changeup that might only be good enough for him to show occasionally might be enough. When Paxton got to the big leagues, he showed a more relaxed and refined delivery, which in turn led to better command.
If Paxton can continue to find the strike zone, a future as a starter awaits, with the Mariners knowing he has the power stuff to succeed in the bullpen if needed.
5. Chris Taylor, SS
Preseason rank: 7
Scouting grades: Hit: 55 | Power: 35 | Run: 50 | Arm: 50 | Field: 50 | Overall: 50
Seattle was very familiar with Taylor, having seen him multiple times while scouting Danny Hultzen in 2011. The club was happy to get Taylor a year later.
Like has often happened with Virginia position players, Taylor has hit better than expected once out of the unfriendly confines of his college home park. He's shown a knack for being patient and he is using all areas of the field. Taylor has gotten a bit stronger, though power is never going to be a big part of his game. He has excellent baserunning instincts, and he has the range and the hands to play shortstop. Some feel his arm might be better at second or for moving around the infield.
The Mariners aren't giving up on Taylor as an everyday guy just yet, pointing to Kyle Seager as an example of a player many felt was destined to a utility career who has now settled in as a starter.
6. Gabriel Guerrero, OF
Preseason rank: 10
Scouting grades: Hit: 45 | Power: 50 | Run: 45 | Arm: 70 | Field: 50 | Overall: 50
Depending on when you see him, Vladimir Guerrero's nephew either looks like a special outfielder who could become as good as his uncle or just an ordinary young kid trying to find his way.
There's no question Guerrero has a very high ceiling. He has very good raw tools, including the ability to hit for average and power, though the latter hasn't shown up in games consistently yet. Guerrero is an aggressive hitter, but like his uncle, he tends to make contact more than you think he should -- though some refinement would allow him to tap into that power more. Guerrero runs fairly well, and he has about as strong an outfield arm as you'll find in the Minor Leagues.
All of Guerrero's skills give him the potential to be the prototypical right fielder when all is said and done, but first he has to show he can use those considerable tools consistently on the field.
7. Austin Wilson, OF
Preseason rank: 13
Scouting grades: Hit: 45 | Power: 50 | Run: 50 | Arm: 60 | Field: 50 | Overall: 50
Since his high school days, Wilson has teased with his tools and his athleticism, but he hasn't always been a consistent performer. The Mariners are hoping he can put it together in their organization.
Wilson is a physical specimen, and he is the kind of player who "looks the part." He has big-time raw power, can run and he has the arm for right field. At the plate, Wilson can be a little bit of a feast-or-famine-type player, and he'll need to make more consistent contact so he can tap into that power more regularly. In the final month of his pro debut in the Northwest League in 2013, Wilson had a .973 OPS, and he continued to build on that during his first full season.
Now healthy after dealing with injuries during his junior year at Stanford, Wilson has the raw tools to fit the right-field profile to a tee.
8. Edwin Diaz, RHP
Preseason rank: 4
Scouting grades: Fastball: 60 | Slider: 55 | Changeup: 40 | Control: 50 | Overall: 50
When Seattle selected Diaz out of Puerto Rico in the 2012 Draft, the club figured it had a project on its hands. It seems, though, that the right-hander is developing more quickly than expected.
Some of Diaz's development has been physical. Diaz has put on around 25 pounds of good weight since his high school days. His fastball and slider are his best offerings, and there might be more in the tank with the heater as he continues to progress. Diaz has improved his fastball command considerably, and his breaking ball is much better than it was, leading to low walk totals and plenty of missed bats. His changeup lags behind, but there is confidence Diaz will master that as well.
With Diaz's stuff and willingness to be a student of the game, he might have as much upside as anyone in the system.
9. Patrick Kivlehan, 3B
Preseason rank: 19
Scouting grades: Hit: 45 | Power: 50 | Run: 50 | Arm: 45 | Field: 45 | Overall: 50
It hasn't been the most direct career path for this Rutgers product, but Kivlehan has an intriguing set of tools he's just learning how to use consistently.
A football player in college, Kivlehan didn't return to baseball until his senior year, where he promptly had a huge season and moved up Draft boards in a hurry. Kivlehan has the tools to be a run-producing third baseman with the ability to hit for average and plenty of power. He runs well for a guy his size, and he brings a football mentality to his game on a daily basis.
Kivlehan had some rough edges due to his time away from the game, but he started to smooth them out in 2013. More reps will help, and the end result could be Kivlehan becoming an everyday corner infielder.
10. Gareth Morgan, LHP
Preseason rank: None (2014 CB)
Scouting grades: Hit: 45 | Power: 60 | Run: 35 | Arm: 55 | Field: 50 | Overall: 50
The Mariners clearly were going after power potential in the early rounds of the 2014 Draft, nabbing Jackson in the first round, then giving Morgan $2 million as the No. 74 overall pick.
Strong and toolsy, Morgan's raw power is undeniable. He has put on shows in showcase batting practices in the past, and he has the ability to hit the ball out of any ballpark. There are some questions about Morgan's ability to hit enough to tap into that power consistently. He is a solid outfielder with a strong arm, giving him a good profile for right field.
The Mariners clearly believed enough in Morgan's bat, and those who dream on him might see a future Giancarlo Stanton type in the future.
11. Ketel Marte, SS
Preseason rank: 16
Scouting grades: Hit: 45 | Power: 30 | Run: 65 | Arm: 50 | Field: 55 | Overall: 45
Pushed aggressively, Marte reached the Class A Advanced California League in 2013 at age 19. The Mariners think he can develop into a top-of-the-order catalyst in the future.
Marte's best tool is his speed, and he has more than enough to be a threat on the basepaths and to give him range up the middle. The Dominican switch-hitter's actions and his arm are good enough for shortstop, but he's also seen time at second base thus far in his pro career. Marte has no power to speak of, relying on making contact and using his speed for his offense. Some added strength and improvement of his on-base skills will certainly help him down the road.
If the bat can come along, Marte has the chance to be an everyday shortstop, though a career as a speedy and dynamic utility type is nothing to sneeze at.
12. Luiz Gohara, LHP
Preseason rank: 5
Scouting grades: Fastball: 60 | Curveball: 50 | Slider: 45 | Changeup: 50 | Control: 45 | Overall: 45
If everything clicks for this young Brazilian lefty, Gohara has the chance to be something special, even if Seattle seems a long way off.
Gohara has everything you want from a southpaw. He has a fastball that reaches up to 93-94 mph, and he has a good curveball to go along with it. Marte also throws a slider, which isn't as good as his other breaking ball, and he shows a really good feel for a changeup. The one thing of concern is that Gohara put on a lot of weight, and it is not the good kind. It's clear he's going to have to work hard on his conditioning to continue his progress.
Gohara is only 17 years old. If he can get in shape, he has the stuff to be a top-flight left-handed pitching prospect.
13. Tyler Marlette, C
Preseason rank: 8
Scouting grades: Hit: 50 | Power: 55 | Run: 30 | Arm: 55 | Field: 50 | Overall: 45
Marlette capped his trip through the showcase circuit in the summer of 2010 with an MVP performance in the Aflac All-America Game at Petco Park. After a slow start to his professional career, he advanced to full-season ball for the first time in 2013.
Marlette's power is his best tool. He creates good bat speed and he can drive the ball to all areas of the field. Marlette is a below-average runner, but he takes advantage of opportunities to be aggressive on the basepaths.
Marlette made big strides on defense in 2013. Combined with his strong arm and his good makeup, the improvements Marlette made to his receiving give him a chance to be at least an average defender. With his power, that would make Marlette an all-around threat.
14. Victor Sanchez, RHP
Scouting grades: Fastball: 55 | Curveball: 50 | Changeup: 50 | Control: 55 | Overall: 45
The Mariners have never been shy about being aggressive in the international market, and they weren't when they gave Sanchez seven figures to sign out of Venezuela.
Unlike some of the hard throwers in the system, Sanchez relies more on command and control. His fastball sits in the low 90s, at best, and he couples it with solid yet unspectacular secondary stuff in his curve and his changeup. Sanchez is a serious strike-thrower, though, keeping the ball down in the zone consistently, which allows his stuff to play up. At 6-foot-0 and 255 pounds, there's no projection here.
Still only a teenager, Sanchez's pitchabilty could allow him to move quickly, even if his ceiling maxes out as a No. 4-type starter.
15. Tyler Pike, LHP
Preseason rank: 9
Scouting grades: Fastball: 50 | Curveball: 50 | Changeup: 55 | Control: 40 | Overall: 45
A combination of a feel for three pitches, deception and athleticism gives Pike the chance to be a solid big league starter, assuming he can find the strike zone more consistently.
Pike built off of a very solid full-season debut as a teenager in the Midwest League in 2013. He'll throw his fastball in the 89-92 mph range, and he has shown an advanced feel for his changeup already. Pike's breaking stuff isn't quite as good, but he has the chance to give him a third solid offering in the future. While hitters have a tough time picking the ball up coming from Pike's hand, he is going to have to improve his fastball command considerably to continue having that kind of success at the higher levels.
The jump up to a higher level should be a good challenge for Pike, with a ceiling as a mid-rotation starter being a possibility.
16. Danny Hultzen, LHP
Preseason rank: 14
Scouting grades: Fastball: 55 | Slider: 50 | Changeup: 55 | Control: 50 | Overall: 45
Taken No. 2 overall in the 2011 Draft, Hultzen was supposed to be an advanced college lefty who would get to the big leagues quickly. He was headed in that direction when shoulder troubles derailed his career.
While Hultzen did have command issues during his first full year in 2012, he did reach Triple-A. But his 2013 season really never got going, as he was shut down twice and he eventually had surgery to repair a torn rotator cuff -- which will keep him out for the '14 season. When healthy, Hultzen has a very good three-pitch mix in his fastball, changeup and slider, and he's shown the ability to command all three in the past.
For now, it's all about Hultzen getting healthy and back on the mound, then it will be time to reassess just what kind of pitcher he can become.
17. Carson Smith, RHP
Preseason rank: 11
Scouting grades: Fastball: 60 | Slider: 50 | Control: 45 | Overall: 45
Relievers who throw from an unorthodox arm angle are often dismissed as being successful because of trickery. When they strike out nearly 12 batters per nine innings, it's time to take notice.
Smith isn't just a guy who throws from a low three-quarters angle. From that slot, he can crank his fastball up into the mid 90s, sitting in the 91-93 mph range. Smith's heater has plus sink to generate a ton of ground-ball outs. He has one of the best breaking balls in the system, a sweeping slider with early break. Smith is especially tough on right-handed hitters, and he went more than a month at the end of 2013 without giving up a run. Because of his arm angle and especially that slider, he reminds some of former reliever Jeff Nelson.
Smith profiles as a seventh-inning or setup-type guy, but he's one who should contribute to the big league bullpen soon.
18. Tyler O'Neil, OF
Preseason rank: 20
Scouting grades: Hit: 50 | Power: 45 | Run: 45 | Arm: 50 | Field: 45 | Overall: 45
A catcher during his amateur days in Canada, O'Neill has made the move to the outfield, with the chance to be a power-hitting corner guy in the future.
O'Neill brings a ton of natural strength to the plate, which should allow him to continue to hit for power. With excellent bat speed, he should be able to hit for average as well. Too big to stay behind the plate, Seattle moved O'Neill to left field during his summer debut in the Rookie-level Arizona League, and that's where he'll stay for the time being. O'Neil will need to work on his defensive play. A move to first isn't out of the question, but in the end, it's his bat that will carry him up the organizational ladder.
The adage goes that if you can hit, you'll find your way to the big leagues. The Mariners hope that is the case with O'Neill as well.
19. Xavier Avery, LHP
Preseason rank: None
Scouting grades: Hit: 45 | Power: 30 | Run: 60 | Arm: 45 | Field: 50 | Overall: 45
When Avery was drafted by the Orioles back in 2008, the question was always about whether the onetime Georgia football recruit could translate his raw tools and athleticism into performance. He made it to the big leagues in 2012, but the Orioles sent him to the Mariners in the Michael Morse deal in August '13.
Avery still has intriguing tools, starting with his outstanding speed that allows him to be a basestealing threat and to cover a lot of ground in the outfield. If his bat can continue to develop, the left-handed hitter could be a top-of-the-order type. Avery will need to make more consistent contact and improve his on-base skills to truly profile as a leadoff hitter.
Avery has the ability to play all three outfield positions, something he's done over the past few seasons after mainly playing center early on his career. A future as a fourth outfielder might be in the cards.
20. Julio Morban, OF
Preseason rank: 17
Scouting grades: Hit: 50 | Power: 45 | Run: 40 | Arm: 50 | Field: 45 | Overall: 45
Injuries have proven to be the main stumbling block for Morban, who originally signed for more than $1 million back in 2008. Despite that, he's shown enough to earn a spot on the Mariners' 40-man roster, and he could be knocking on the door soon.
Morban was having a solid 2013 season, his first above Class A ball, when he broke his leg in August. Morban has yet to log more than 400 at-bats in one season, but he's shown some ability to hit for average to go along with some extra-base pop. He's played all over the outfield, mostly in right in 2013, but he probably profiles best defensively in left. Morban does have the hitting profile that teams like to see in corner guys.
The biggest thing is for Morban to turn in a healthy season. That could lead to his first trip to Seattle.