Mariners in AFL: O'Neill aims to end year on high note

MLB Pipeline checks in on Seattle's prospects in the Arizona Fall League

Mariners in AFL: O'Neill aims to end year on high note

Tyler O'Neill put himself on the map with a powerful 2015 campaign that saw him slug 32 home runs in 106 games for Class A Advanced Bakersfield. It was an eye-opening performance, but scouts wanted to see more progress from O'Neill, especially outside the hitter-friendly California League, before fully buying in.

The Mariners' No. 2 prospect checked every box this year in his first Double-A campaign, batting .293/.374/.508 with 24 home runs and a league-leading (and career-high) 102 RBIs for Jackson. O'Neill's impressive season netted him Seattle's Ken Griffey Jr. Minor League Hitter of the Year award and he was named Southern League MVP.

O'Neill would add to his accolades in the Southern League playoffs, as he earned Finals MVP honors after hitting .429 with six hits and three RBIs in Jackson's three-game sweep of Mississippi. However, the 21-year-old outfielder is quick to acknowledge that it was his team's year-long effort, not just his own, that led to the title.

O'Neill on Fall League ASG

"Great year all together," O'Neill said. "We had a great first half, clinched a playoff spot and all the boys really came together in the end during the playoff push. We did a great job down there."

Complete Arizona Fall League Coverage

But in spite of his successes, O'Neill understands that he still has a ways to go in terms of his overall development. It's why he was eager to return to the Arizona Fall League this year after receiving his first taste of the circuit in 2015.

"I just want to become a better overall player," said O'Neill, who hit .333 with three homers with five RBIs over eight games for Peoria in his first AFL stint. "I think anyone can work on bettering themselves in every category. So more reps, more hitting, more defensive plays -- everything."

O'Neill, MLBPipeline.com's No. 59 overall prospect, certainly has bettered himself in his second go-round in Arizona, where, through 11 games, he's hitting .313 with three home runs and nine RBIs for the Javelinas.

Meanwhile, O'Neill believes that the Mariners allowing him to develop as an outfielder, after he reportedly had been considered as a catcher by multiple teams, has been instrumental towards his progress at the plate.

O'Neill on improving overall

"A couple teams didn't want me behind the plate, others did," he said. "But Seattle took me and threw me in the outfield, and I've been working there ever since."

Much like with his hitting, O'Neill has made strides in the outfield as he's climbed the Minor League ladder. This past season, the British Columbia native recorded a career-high 10 outfield assists (nine in right field), doubling his total from the previous year.

O'Neill's stock continues to trend in the right direction as he prepares for the move up to Triple-A Tacoma next season, not to mention a potential big league debut with the Mariners.

Mariners hitters in the Fall League

Guillermo Heredia, OF
Drew Jackson, SS
Tyler Marlette, C
O'Neill

Signed by Seattle last March, Heredia went on to appear in 45 games with the Mariners, hitting .250/.349/.315 with four extra-base hits and 12 RBIs in 45 games. The 25-year-old outfielder has begun the Fall League on a tear, as he's already tallied five extra-base hits in five games while pacing the Javelinas in all three triple-slash categories (.412/.545/.882).

Jackson's performance this season at Bakersfield wasn't on par with his 2015 pro debut in the Class A Short-Season Northwest League, but it was still plenty encouraging. The 2015 fifth-rounder hit .258/.332/.345 with 32 extra-base hits and 16 steals, while his 87 runs scored ranked third in the circuit.

Jackson on making adjustments

"This year didn't go as well as I wanted it to, but there were still a lot of positives to take from it and a lot of things I learned that I need to work on," Jackson, the Mariners' No. 3 prospect, said. "I'm lucky to have our hitting coach, Brant Brown, here, so we've been working a lot in the cages and during batting practice."

Marlette is back in the Fall League for a second straight year so that the Mariners can get an extra look at the 23-year-old backstop before December's Rule 5 Draft. He's coming off of a strong offensive campaign, during which he batted .273/.335/.472 with 14 home runs at Bakersfield before advancing to Jackson, although his defense behind the plate remains a work in progress.

Mariners pitchers in the Fall League

Luis Gohara, LHP
Emilio Pagan, LHP
Dylan Unsworth, RHP
Thyago Vieira, RHP

The youngest pitcher on a Fall League roster, Gohara, 20, turned in a breakout performance this season as he made three dominant starts for Everett before joining Class A Clinton, where he posted a 1.82 ERA with 60 strikeouts in 54 1/3 innings (10 starts) down the stretch. The Mariners' No. 5 prospect has been equally impressive in Arizona, where he's operated in the high 90s with his fastball while touching triple digits periodically across six outings.

Pagan, 25, was sharp in his first taste of the high Minors, as he recorded 10 saves in 11 chances and posted a 2.49 ERA across 41 appearances between the Double- and Triple-A levels. The 6-foot-3 left-hander also limited hitters to a .197 average, with 84 strikeouts and 29 walks in 65 innings.

Injuries prevented Unsworth from suiting up for the World Team in this year's SiriusXM All-Star Futures Game. A mid-season All-Star in the Southern League, the 24-year-old right-hander from South Africa is using the Fall League to make up for lost time after he logged just nine starts for Jackson -- none after June 7 -- during the regular season.

Owner of arguably the best fastball in this year's Fall League, Vieira has averaged 99-102 mph with his heater and reportedly bumped 104 mph in his first outing for Peoria. The Brazilian right-hander's mid-80s curveball leaves something to be desired, and he'll need to clean it up for his success to translate at more advanced levels.

Mike Rosenbaum is a reporter for MLB.com. Follow him on Twitter at @GoldenSombrero. This story was not subject to the approval of Major League Baseball or its clubs.