BOSTON -- As gloomy as the skies were at Fenway Park on Thursday, you couldn't tell by the sunny disposition of left-hander Jon Lester. And who could blame him?

After being shut down since May 3 because of some cramping in his left forearm, Lester has been given clearance to resume his rehab program at Triple-A Pawtucket. Lester will take the ball on Saturday night in Ottawa, once again putting in motion his courageous comeback from anaplastic large cell lymphoma.

The final hurdle was cleared on Wednesday, when Lester pitched a side session that also included three at-bats against simulated hitters.

"It felt good," Lester said. "Everything came out fine, like we expected. We just wanted to make sure that later down the road, this doesn't happen again. Now we just step forward and get the pitch count back up and go from there."

Because he was sidetracked by the cramping, the clock will go back to 30 days on Lester's rehab assignment. The final day of that assignment would be June 17, though it's conceivable that the Red Sox could insert Lester into the rotation before that.

If it were up to Lester, he'd be making his 2007 debut long before that.

"Tomorrow, but that's not going to happen," he said. "Since the season started, I've wanted to be here. Obviously, they have a plan, and their biggest concern is my health, not only with my arm but my overall health. They want to take it slow and get the pitch count up. Hopefully, this time we can do that without any problems."

Manager Terry Francona estimates that Lester will throw 50 to 55 pitches in Saturday's start.

"And he must be feeling good, because he's really fighting us on that," Francona said. "He's ready to throw 100. That's probably really good."

Drew recovering nicely: A day after slamming his lower back into the bullpen wall in an unsuccessful attempt to stop a home run, right fielder J.D. Drew seemed to be doing OK. Had Wednesday's game been played, Drew would have been on the bench. It's unclear if he'll play in Thursday's doubleheader.

"He checked in this morning and said he was doing pretty well, which was good news," Francona said. "I kind of thought he'd wake up feeling like he got hit by a wall. And then he got to the ballpark and said, 'I don't feel any worse now than I did when I left the game last night.' I think that's encouraging.

"Does that mean he's going to play [on Thursday]? I don't know. We'll see. I think the news is more good than bad. I think he hit the wall pretty hard last night and in kind of a weird way only that wall can do, because of the size of it and the height of it. He's sore, but I don't think anything more than sore."

Snyder provides relief: It was no slight to Kyle Snyder that the Sox didn't call on him to start Friday's game in place of the injured Josh Beckett. In fact, it was more a reflection of the quality job Snyder is doing out of the bullpen, posting a 1.98 ERA in 12 outings. Snyder also hasn't been stretched out enough to expect a lengthy start.

"We like him in his role," Francona said. "Again, there's some trickle-down effect. 'Snydes' can pitch, he gets outs. We like the way he gets outs. But he's been more of a one- to two-inning guy. If we try to go three or four, it's not deep enough into the game where, even though we think he can pitch well, you're going to go through the whole bullpen. This way we'll have somebody, and then we'll keep our bullpen intact, which is important. It's not a confidence issue with Snydes. It's probably the opposite."

On deck: The Red Sox and Tigers will complete this four-game series with a day-night doubleheader on Thursday. The first game is slated for 12:35 p.m. ET, with Julian Tavarez facing Mike Maroth. Curt Schilling goes against Chad Durbin in the 7:05 p.m. nightcap.