Whitley, who has been rehabbing from Tommy John surgery, was claimed off waivers by the Rays from the Yankees in November. In two Major League seasons with the Yankees, he went 5-5 with a 5.02 ERA in 28 games (16 starts).
Rays manager Kevin Cash said Whitley will work out of the bullpen, but his stints will be planned ahead of time due to the fact he's returning from Tommy John surgery. They don't want Whitley to endure the demands of being a reliever, which entails warming up on the spot in anticipation of entering the game.
Mahtook was hitting .305 with a home run and seven RBIs in 27 games for the Bulls. In 43 games with the Rays, he's hitting .158 with a home run and seven RBIs.
Shaffer was hitting .227 with 11 home runs and 48 RBIs for the Bulls. With the Rays this season, he's hitting .286 in five games.
Geltz is 0-2 with a 3.03 ERA in 31 appearances for the Bulls and 0-2 with a 6.86 ERA in 22 appearances for the Rays, allowing 10 home runs in 21 innings.
Marks is 7-11 with a 3.86 ERA in 25 games for the Bulls (23 starts). This will be his first stint in the Major Leagues since his first and only big league appearance in 2014 with the Royals.
Conger began the season with the Rays, hitting .194 with three home runs and 10 RBIs in 49 games. He struggled behind the plate, too, throwing out just eight of the 43 who attempted to steal against him. The catcher's offensive struggles continued at Durham, where he hit .165 with three home runs and 11 RBIs in 30 games.
Bill Chastain has covered the Rays for MLB.com since 2005. This story was not subject to the approval of Major League Baseball or its clubs.