Okay, maybe just a bit of speculation…

On April 15, Oswalt left his start after six innings, after straining his back while fielding a bunt. Six days later, he pitched his best game of the season, with six innings of one-hit ball against the Padres. So what happened Monday night? From MLB.com’s Barry Bloom:

“He was all right,” Phillies manager Charlie Manuel said when asked after that game if Oswalt was having any physical problems. “His stuff wasn’t good. His stuff wasn’t crisp. His velocity was down. I figured there was no sense leaving him out there.”

Any question about that back?

“Ah, no,” Manuel said. “He didn’t say anything about that.”

We should probably take everyone at their word. But Oswalt hasn’t thrown more than six innings in a game this season, and he’s topped 90 pitches just once. And Monday’s performance — three innings, zero strikeouts — suggests that maybe he was hurting last night. Or was distracted.

Or maybe it’s a complete coincidence, with no connection between a terrible outing and leaving his team before the clubhouse doors opened after the game.

We’ll know soon enough.