"He was able to throw his bullpen without any complications," manager Bob Melvin said, "though there were times when he felt it just a little bit. Going after it in a bullpen with the intensity he did, we'll wait until tomorrow to see how he feels before we make a decision on whether or not he starts on Thursday.
"After he would let the ball go and take a step or so, there were times he said it felt a little bit tight, but it wasn't precluding him from throwing the ball in the fashion, mechanically, that he normally does. So we'll just kind of wait and see."
Parker will play catch on Wednesday, but how he runs will truly indicate his readiness for a start the next day. Should he be unable to go on schedule, the A's are likely to turn to either Dan Straily, who was expected to be recalled Saturday for a start in Kansas City, or top pitching prospect Sonny Gray, who was scratched from his Tuesday start for the River Cats -- presumably as insurance for Parker.
Parker then could potentially start Saturday if the A's decide he needs an extra couple of days of rest.
"I think it'll be pretty evident tomorrow," Melvin said. "If there's some soreness, we probably won't mess with that. If we feel it's all cleared up, then we'll go ahead and start him on Thursday. We're not going to make a decision until we have to."
Jane Lee is a reporter for MLB.com. Read her blog, Major Lee-ague, and follow her on Twitter @JaneMLB. This story was not subject to the approval of Major League Baseball or its clubs.