This is the first big league stint for the 27-year-old Castillo, who signed a seven-year major league contract with Boston on August 23. The right-handed batter hit .293 (12-for-41) with seven runs scored, four doubles, a home run, five RBI, five walks, and two stolen bases in 11 minor league games to begin his U.S. pro debut, all in playoff action between Triple-A Pawtucket (5 games), Double-A Portland (4 games), and the Rookie-level Gulf Coast League Red Sox (2 games). He helped two of those affiliates, the PawSox and the GCL Red Sox, to championships in their respective leagues. In 360 games over five seasons in Cuba's major league, Serie Nacional, Castillo hit .319 (403-for-1,265) with 75 doubles, 11 triples, 51 home runs, 99 walks, 256 runs scored, and 76 stolen bases. He spent all five campaigns with his hometown team, Ciego de Avila, and last played in Serie Nacional during the 2012-13 season.
For Brentz, 25, this marks the first major league stint of his career. In 63 regular season games for Pawtucket this year, he batted .243 (56-for-230) with 11 doubles, 12 home runs, 53 RBI, and a .341 on-base percentage. The right-handed hitter also went 10-for-38 (.263) in eight postseason games for the PawSox. Brentz landed on the disabled list on May 20 (retroactive to May 16) with a right hamstring strain and was activated on August 2 after playing in nine rehab games between the GCL and Short-A Lowell. After returning from the DL, he hit .263 (35-for-133) with six homers and 27 RBI between regular and postseason play. Rated Boston's No. 3 outfield prospect by Baseball America entering this season, Brentz has totaled 83 home runs and 326 RBI in five seasons in the Red Sox' system. The native of Crossville, TN was selected by the Red Sox in the supplemental round (36th overall) of the 2010 June Draft.
Cecchini, 23, rejoins Boston for his third career major league stint, all this season. He has appeared in one game for the Red Sox this year, going 1-for-2 with an RBI double in his major league debut on June 1 against the Tampa Bay Rays. The left-handed batter hit .263 (107-for-407) with 21 doubles, one triple, seven home runs, 57 RBI, and 44 walks in 114 regular season games for Pawtucket this year, leading the club in RBI and ranking second in hits, walks, runs (52), and total bases (151). Defensively, he appeared primarily at third base (84 games), with 26 games played in left field. In his last 30 contests from August 9 through the end of the playoffs, Cecchini hit .357 (40-for-112) with 12 doubles, a triple, two homers, and 26 RBI, including a .306 mark (11-for-36) in nine postseason games while helping the PawSox to the Governors' Cup title. A native of Lake Charles, LA, he was signed by the Red Sox as a fourth-round selection in the 2010 June Draft.
Escobar, 22, begins his third stint in the majors with Boston this season. Acquired from the Giants on July 26 along with Hembree, Escobar has worked out of the starting rotation for Pawtucket. In five regular season starts for the PawSox, he was 0-2 with a 4.28 ERA (13 ER/27.1 IP), but in his three starts for the PawSox in the playoffs, Escobar was 1-0 with a 2.18 ERA (5 ER/20.2 IP) with two walks and 18 strikeouts. He entered this season as the No. 2 overall prospect in the Giants minor league system as rated by Baseball America. Escobar's only appearance for the Red Sox came on August 27 at Toronto where he faced only three batters in 1.0 scoreless inning for his major league debut.
Hembree, 25, returns to the Red Sox for his third major league stint of the season. Following his acquisition from the San Francisco Giants on July 26, he appeared in 12 games for Pawtucket between the regular season and postseason going 1-1 with 4 saves, a 2.13 ERA (3 ER/12.2 IP), and 15 strikeouts. Those numbers include a 1.50 ERA (1 ER/6.0 IP) and two saves over five games for the PawSox in the Governor's Cup playoffs. With Boston, Hembree has appeared in three games, posting a 4.50 ERA (3 ER/6.0 IP). A 2014 Pacific Coast League mid-season All-Star, Hembree entered this season as the No. 7 overall prospect in the Giants organization according to Baseball America.
Lavarnway, 27, begins his second major league stint of the season. The right-handed hitter spent the majority of the year at Pawtucket, batting .283 (62-for-219) with 10 doubles, three homers, 20 RBI, and 22 runs scored in 62 regular season games. Defensively, he appeared in 31 games at first base and 15 at catcher. He was recalled to Boston on May 26 and went 0-for-4 in four games with the Red Sox before being placed on the disabled list on May 30 with a left hamate fracture. He played in 14 games over two rehab assignments between the GCL Red Sox, Portland, and Pawtucket, and was activated and optioned to the PawSox on August 14. Over his last 26 Triple-A games overall, including rehab, regular season, and postseason, he hit .316 (30-for-95) with two home runs and 15 RBI.
With today's moves, Boston's active major league roster is now at 38.