A left side strain has held Fister out since May 28. He said he felt stiff when he started, but much better as the session went on.
"Once it loosened up, I threw a couple pitches and didn't feel it again," Fister said. "We're going to take it day by day and find out how I feel [Thursday]."
Head athletic trainer Kevin Rand said the bullpen session went "very well," and Fister will be re-evaluated Thursday. Fister said he's not sure when the plan for return is, but he may know more after seeing how he feels Thursday.
"Taking a good step in the right direction is definitely exciting," he said. "I don't want to rush it, don't want to baby it."