"It's kind of unpredictable," McHugh said. "I could see them going either way with it for the next start."
If McHugh can't pitch Saturday, they'll likely move up Jarred Cosart to throw Saturday and Brad Peacock to throw Sunday considering the club has day off on Thursday.
"If he makes it through with no problems, he's still in the rotation," Porter said. "We'll wait until after [Thursday] to make a decision."
McHugh (4-8) has lost his last five starts, but he hasn't pitched too poorly in that span. He's 0-5 with a 4.18 ERA in 28 innings, having allowed just 21 hits while striking out 33 innings batters.
Brian McTaggart is a reporter for MLB.com and writes an MLBlog, Tag's Lines. Follow @brianmctaggart on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.