"He went up off the mound yesterday and he wasn't ready to really let it go full," Tigers head athletic trainer Kevin Rand said Wednesday afternoon. "We're backing off him for a couple of days here and giving him a chance to kind of regroup a little bit."
Rand said Fister cut the session short because he had some pain in his abdomen.
Fister threw for the first time since going on the 15-day disabled list April 8 for a left costochondral strain on Tuesday. He is eligible to return to the roster on Monday, but it doesn't appear he'll be ready to pitch.
Fister, 28, was traded from the Seattle Mariners to Detroit during last season. In 10 starts, he compiled an 8-1 record with an ERA of 1.79.