Beckett hasn't pitched in a game since June 11 because of right shoulder inflammation. His return means the team may carry a six-man rotation into the All-Star break, which, after Tuesday night's game, is 11 games away.
Beckett threw a bullpen session prior to Monday's series opener vs. the Blue Jays. Valentine said Beckett told him the shoulder felt great.
"I'm considering it. Until the All-Star break?" Valentine said of the six-man rotation. "Yeah. I think there's a situation where, depending on how we slot Josh in, I think it can benefit everyone to get a little creative there until the All-Star break."
Beckett is 4-7 with a 4.14 ERA in 12 starts this season.
Valentine said Daisuke Matsuzaka, who started Tuesday and went 5 2/3 innings in a no-decision, would make his next start during a three-game series in Oakland next week.