Geltz is 0-2 with a 3.31 ERA with three saves in 29 appearances with the Bulls this season.
Mahtook has struggled with his offense, but appeared to be coming out of his funk as he got the game-winning hit on Thursday against the Red Sox and hit his first home run of the season on Friday night.
Mahtook is hitting .158 with a home run and seven RBIs this season.
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.