The concern is a sore right elbow that has gotten progressively worse over the past few starts. Bonderman has now lost eight of his last 10 starts as his ERA has risen from 3.48 at the All-Star break to a season-worst 5.01 after allowing six runs on seven hits against the Mariners.
"I'm disappointed, scared, nervous," Bonderman said. "I really don't know exactly what's going on. I'm just hoping that it's nothing major."
The injury is unclear because there isn't a clear-cut explanation, though Bonderman said he was a bit encouraged that the pain is on the backside of the elbow. He said he and the training staff seem to think the location of the injury means it hopefully isn't a major one.
Bonderman said the pain has been in his elbow "for a while now," though he didn't fully admit the elbow was bothering him until his last start against the White Sox.
"I did everything I could, whatever I could do, to get back on the mound, and so far, I did it," Bonderman said. "I'm just frustrated not to pitch in a pennant race. To get out and pitch poorly makes it worse. [I'm] just disappointed in the whole situation."
His reputation as a player that plays through pain -- Leyland referred to the fifth-year pitcher as a soldier -- may have caused Bonderman to continue to start every fifth day even though he knew he wasn't completely healthy. He would still like to return this season, as the Tigers now trail the Yankees by four games in the American League Wild Card with 19 games to play.
"If they shut me down the rest of the year, it is what is, but I would like to be able to come back and pitch," Bonderman said.
A similar circumstance with Bonderman's elbow occurred in 2005. The Tigers -- then managed by Alan Trammell -- also decided to pull him from the rotation, though he came back healthy last year and made a career-high 34 starts with 202 strikeouts.
He said the velocity in his pitches -- he hit 94 mph on Sunday -- is still there, but the bite on his slider and sinker is not.
"I just can't get can't get extended all the way on each of my pitches," Bonderman said.
The extent of the injury will become a bit clearer on Monday, when Bonderman undergoes a series of more thorough examinations by the Tigers training staff.
"I don't know, we're going to look into it a little further," Leyland said. "I don't have anything on it right now other than I know that it's not right. I'll probably shut him down. Possibly. Probably. We'll wait and see."