Instead of pitching in his regular turn Wednesday night in Yankee Stadium, Buchholz will be pushed back to Friday night in Toronto.
Tim Wakefield will take Buchholz's scheduled start against the Yankees on Wednesday night.
Buchholz has had a sore back for a little while, Red Sox manager Terry Francona said in his pregame meeting with the media. In his last start, Wednesday against the White Sox, Buchholz was tagged for eight hits and six runs, five of them earned, in only 4 2/3 innings.
"It hasn't interfered with his pitching, but he wasn't quite reaching," Francona said, meaning Buchholz wasn't extending to the fullest in his delivery. "Buck owned up to it. He said it [his back] didn't hurt, but he thought it would hurt [if he extended].
"So we'll give him two extra days, let him start his five-day cycle two days late," said Francona. "It makes sense. I know he wanted to pitch in New York. It's a great place to pitch, a great atmosphere. But he knows this is in his best interests."
Buchholz is 4-3 with a 3.82 ERA this season.
Steven Krasner is a frequent contributor to ESPNBoston.com.