Using a sinking fastball that ranges from the low to mid 90s, Martin is one of the best strikeout pitchers in the Red Sox's farm system. Pitching the entire 2016 season at Triple-A Pawtucket, Martin converted all six of his save opportunities while posting a 3.38 ERA in 66 2/3 innings.
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Martin notched 10.53 strikeouts per nine innings in his 36 appearances and held opponents to a .154 average with runners in scoring position, including 0-for-10 with the bases loaded.
Ysla, who hails from Venezuela, was acquired from the Giants on Aug. 31, 2015, for outfielder Alejandro De Aza.
The 24-year-old made all but one of his 40 appearances in 2016 for Double-A Portland and pitched once for Triple-A Pawtucket at the end of the season. With a low arm slot, Ysla's delivery can be tough to pick up. His fastball lives in the 90s.
In 2016, Ysla pitched exclusively out of the bullpen for the first time in his career, going 2-5 with a 3.99 ERA and racking up 62 strikeouts in 56 1/3 innings. He pitched his best from June 1 on, holding opponents to a .208 average.
None of Boston's Top 30 prospects are eligible to be selected in the Rule 5 Draft.
The Red Sox did not add outfielders Allen Craig or Rusney Castillo to the 40-man roster, but the salaries for both players would likely prohibit either of them from being selected in the Rule 5 Draft.
Craig, a World Series hero for the Cardinals in 2011, is owed $11 million in 2017. The Red Sox have a $1 million buyout for his $13 million club option in '18. In '16, Craig did not play in the Majors at all for the first time since he broke with the Cardinals in '10.
With much fanfare, the Red Sox signed Castillo to a seven-year, $72.5 million contract in August 2014. But the right-handed hitter from Cuba hasn't been able to make the necessary adjustments and was taken off the 40-man roster midway through last season. The Red Sox still owe Castillo $46 million, and he is on the payroll through the '20 season.
MLB requires teams to add players who signed at age 18 or younger to 40-man rosters within five professional seasons, or those who signed at 19 or older within four seasons, or they will become eligible for other organizations to draft. Clubs pay $50,000 to select a player in the Major League phase of the Rule 5 Draft, slated for Dec. 8. If that player doesn't stay on the 25-man roster for the full season, he must be offered back to his former team for $25,000.
The Red Sox's 40-man roster is as follows:
PITCHERS (22): Fernando Abad, Matt Barnes, Clay Buchholz, Roenis Elias, Heath Hembree, Williams Jerez, Brian Johnson, Joe Kelly, Craig Kimbrel, Martin, Henry Owens, Drew Pomeranz, Rick Porcello, David Price, Noe Ramirez, Eduardo Rodriguez, Robbie Ross Jr., Robby Scott, Carson Smith, Brandon Workman, Steven Wright, Ysla.
CATCHERS (4): Bryan Holaday, Sandy Leon, Blake Swihart, Christian Vazquez.
INFIELDERS (9): Xander Bogaerts, Marco Hernandez, Brock Holt, Deven Marrero, Yoan Moncada, Dustin Pedroia, Hanley Ramirez, Pablo Sandoval, Travis Shaw.
OUTFIELDERS (5): Andrew Benintendi, Mookie Betts, Jackie Bradley Jr., Bryce Brentz, Chris Young.