BOSTON, MA—The Boston Red Sox today acquired minor league infielder Christian Koss from the Colorado Rockies, in exchange for minor league left-handed pitcher Yoan Aybar.

The Red Sox’ 40-man roster is now at 39.

Chief Baseball Officer Chaim Bloom made the announcement.

Koss, 22, was ranked by Baseball America as the Rockies’ No. 29 prospect. Selected in the 12th round of the 2019 June Draft, the right-handed hitter was named a mid- and post-season All-Star in the Rookie-level Pioneer League in 2019. He was tabbed MiLB.com’s Pioneer League Player of the Month for July and twice earned the league’s Player of the Week honor. In 53 games for Grand Junction, Koss hit .332 (63-for-190) with 11 home runs, 51 RBI, 10 stolen bases, and a 1.050 OPS, making 18 starts at third base, 18 at second base, 13 at shortstop, and four as a designated hitter. Born in Riverside, CA, he attended the University of California, Irvine.

Aybar, 23, was signed by the Red Sox in July 2013 and began his professional career as an outfielder. Since beginning the 2018 season as a pitcher, the left-hander has gone 3-4 with a 4.45 ERA (42 ER/85.0 IP) in 61 appearances, all in relief.

BOSTON RED SOX 40-MAN ROSTER (39)

PITCHERS (20): Matt Barnes, Eduard Bazardo, Ryan Brasier, Colten Brewer, Austin Brice, Nathan Eovaldi, Jay Groome, Darwinzon Hernandez, Tanner Houck, Bryan Mata, Chris Mazza, Joel Payamps, Nick Pivetta, Eduardo Rodriguez, Chris Sale, Connor Seabold, Jeffrey Springs, Josh Taylor, Phillips Valdez, Marcus Walden

CATCHERS (4): Deivy Grullón, Kevin Plawecki, Christian Vázquez, Connor Wong

INFIELDERS (9): Jonathan Araúz, Christian Arroyo, Xander Bogaerts, C.J. Chatham, Michael Chavis, Bobby Dalbec, Rafael Devers, Dustin Pedroia, Hudson Potts

OUTFIELDERS (6): Andrew Benintendi, J.D. Martinez, Yairo Muñoz, Jeisson Rosario, Alex Verdugo, Marcus Wilson