"He had a headache from being dehydrated," Francona said on Sunday. "The hope is that he rallies enough where maybe he can play catch today a little bit. If he can't, then we've got to start thinking, 'Is Tuesday in question?' And if Tuesday's in question, then we have to make a roster move. I think we're hoping that he's OK."
"I'm feeling better," Bauer said after Sunday's 8-6 loss to the Tigers. "I'm still kind of weak, because you miss a full days' worth of nutrition. ... I'm definitely going in the right direction, but need to get some food in me and get my energy level back up."
Lefty TJ House was originally slated to start on Tuesday, but he was an emergency replacement for Bauer on Saturday after the righty was too sick to pitch. Right-hander Danny Salazar's regular turn to start falls on Wednesday against the Royals, and House would likely be the probable starter for Thursday. Righty Zach McAllister, who opened the year in the rotation, is currently in the bullpen.
Through three starts this season, Bauer is 2-0 with a 0.95 ERA and 26 strikeouts in 19 innings.
Jordan Bastian is a reporter for MLB.com. Read his blog, Major League Bastian, and follow him on Twitter @MLBastian. This story was not subject to the approval of Major League Baseball or its clubs.