Krol, 24, split last season between Detroit and Triple-A Toledo, appearing in 33 games out of the bullpen for the Tigers. The 6-foot-1, 210-pound native of Hinsdale, Ill., went 2-3 with a 5.79 ERA (18 ER/28.0 IP) at the Major League level, striking out 26 while walking 17. Krol finished 1-1 with a 2.30 ERA (8 ER/31.1 IP) in 28 games for the Mud Hens.
Originally drafted in the seventh round of the 2009 First-Year Player Draft by Oakland, Krol was dealt to Washington in 2013 and made his MLB debut that season. He was sent to Detroit that December as part of a three-player package for Doug Fister. In 110 career Major League games out of the bullpen, the left-hander is 4-4 with a 4.91 ERA (48 ER/88.0 IP) and 76 strikeouts.
Speier, 20, spent last season with Single-A West Michigan, pitching exclusively in relief and going 4-2 with a 2.86 ERA (14 ER/44.0 IP) in 33 games. The Tigers acquired Speier, along with Yoenis Cespedes and Alex Wilson, last offseason in exchange for Rick Porcello.
Selected out of Dos Pueblos (CA) High School in the 19th-round of the 2013 First-Year Player Draft by Boston, Speier owns a 7-2 record with a 2.34 ERA (20 ER/77.0 IP) and a 4.9 SO/BB ratio (68 SO/14 BB) over 45 professional games (eight starts).
Maybin, 28, hit a career-best .267 with 10 home runs and 59 RBI in 141 games for the Braves last season.