Fiers was hit by a comebacker off the bat of Mason Williams in the top of the second inning. Fiers was able to finish that inning, but Drew VerHagen relieved him to start the third. X-rays were negative.
"It wasn't too bad -- it is just a bruise -- but I couldn't really land on it," Fiers said. "The guys here didn't want to risk me changing my delivery and hurting my arm."
It is unclear whether Fiers will make his next scheduled start.
"We're going to see how he is," manager Ron Gardenhire said. "It swelled up pretty big."
Fiers is 7-6 with a 3.48 ERA. He has pitched well enough that he was considered a candidate to be traded at the deadline, but the Tigers didn't move him.
Information from The Associated Press was used in this report.