Guthrie was released from the hospital earlier today after being treated for a form of pneumonia. Brad Bergesen is taking Guthrie's turn on the mound tonight.
"I'm not sure if he's going to show up at the park or not," Showalter said of Guthrie, who tossed eight scoreless innings in Friday night's season-opener against the Rays. "Dr. (William) Goldiner, our team physician, has got his arms around it and I think they've got an idea what they're dealing with. Obviously, a form of pneumonia.
"Our next need there would be Sunday. That's still very tentative at this point, until we have an idea what we're dealing with over the next couple of days."
The Orioles would summon a pitcher from Triple-A Norfolk to make Sunday's start if Guthrie can't do it. Chris Jakubauskas would be working on normal rest after starting yesterday against Norfolk State.