Gallagher rejoined the team Friday and played catch from 120 feet. After a little early soreness, Gallagher said he felt fine -- a promising sign that he and the disabled list won't have a date anytime in the near future.
"On the first couple throws it was still there, but it wasn't nearly as bad as it has been in the past," said Gallagher, sporting a bulky icepack on his throwing shoulder. "After that, I got loose, got the blood flowing and then it felt great thereafter."
Originally scheduled to start Saturday, the 22-year-old right-hander is tentatively penciled in to start Thursday afternoon in Oakland against the Rays. He will have a light bullpen session Sunday before his normal, heavier session Tuesday.
Gallagher said he had felt soreness in the shoulder for at least two weeks before the MRI, but he never felt any pain during an actual game -- only when he was warming up. After he was shelled for five runs in just three innings Monday at Toronto, Gallagher, in search of an "ease-of-mind point of view," brought the problem to the A's attention.
"I just wasn't myself," Gallagher said of Monday's start, which resulted in his fifth loss of the season. "I didn't have my location and I didn't have velocity on some throws.
"Maybe I just tired it out or maybe I just tried to fight it for too long," Gallagher said. "I just realized after [Monday's game] that I couldn't keep going the way it was. I had to get something done."
Acquired from the Cubs in the Rich Harden trade, Gallagher said he will try to be less aggressive on his off-day throwing sessions -- a reflection of how the Cubs and A's differ in preparing their starting pitchers.
"The way I'd done things before, I would just go out and throw, throw, throw -- throwing to get loose," he said. "Now, we're kind of learning to get loose to throw."
Andrew Gribble is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.