That means Jake Peavy will get the nod in Game 3 on Saturday.
Buchholz missed three months of the season with neck and shoulder injuries.
He did make four starts in September and has a 5.40 ERA in 16.2 innings pitched this postseason, giving up 19 hits and three home runs.
"It's just a little dead at certain points," he said to ESPN.com. "It's not like a pinpoint straight spot where I can say, 'Yeah, there it is.' It's just general."
Buchholz said said his arm fatigue is nothing out of the ordinary, but wants to be his best and is working to get back to that point.
"After we went through some work today, [Buchholz] did throw a little bit in the outfield, we'll probably look to give him every extra day we can, and that would point to Sunday being Game 4," Red Sox manager John Farrell said.