It was Saupold's fifth game since being called up. The 26-year-old right-hander, signed as an amateur free agent four years ago, has allowed eight runs on 13 hits over six innings with three walks and eight strikeouts. Saupold picked up his first Major League win May 15 with 2 2/3 scoreless innings in the Tigers' comeback victory at Baltimore.
Saupold will undergo tests once the Tigers return to Detroit to determine the severity of the strain.
Taking Saupold's spot will be right-hander Bobby Parnell, with his contract purchased from Triple-A Toledo. The former Mets reliever signed a Minor League deal with Detroit in February and served as the Mud Hens' closer early in the season, recording four saves.
Parnell has given up 12 runs (nine earned) on 21 hits over 20 1/3 innings, good for a 3.98 ERA. He has 11 walks and 16 strikeouts.
"He had thrown well earlier, went through a couple bad outings, and then recently has pitched well again," manager Brad Ausmus said.
The callup comes on the same day Parnell had an opt-out in his Minor League contract that allowed him to ask for his release if he hadn't been called up to the Majors. However, Ausmus said the opt-out wasn't the reason for the call, that Parnell was the recommendation of Mud Hens manager Lloyd McClendon.
"We called Mac just to see who he thought could help us," Ausmus said, "and Parnell was the guy. It ends up working that way, but that [opt-out] wasn't the reason."
The Tigers could get further relief depth in the coming days if they decide to use Shane Greene out of the bullpen upon his return from the disabled list.
To make room for Parnell on the 40-man roster, Detroit designated right-hander Jose Valdez for assignment. The 26-year-old pitched in seven games for the Tigers last year, but he opened this season at Toledo before being demoted to Double-A Erie.
Jason Beck has covered the Tigers for MLB.com since 2002. Read Beck's Blog, follow him on Twitter @beckjason and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.