Yet, his manager thinks Lester's best days are still to come.
Lester (4-0, 4.47 ERA) will make his ninth start Wednesday in the series finale against the Rays. The left-hander is coming off his best outing of the season, when he held the Orioles scoreless over seven innings while allowing just four hits last Friday at Camden Yards.
"It wasn't just his effectiveness," Terry Francona said Tuesday. "It was the way the ball came out of his hands, it's actually been the last two [starts]. Velocity seems to be coming back without effort, tightness to his cutter, changeup. I'm the sure the ball coming out of his hand like he's accustomed to is leading to some confidence. I wouldn't doubt that for one minute."
Lester's seven innings last Friday matched a season-best, going the same distance on Aug. 14 vs. Tampa Bay. Francona said Tuesday that Lester continues to gain strength, along with velocity and command of his four-seam and cut fastballs.
"I've seen him make how many ever starts he made last year and we don't know what he was battling," Francona said. "Nobody knows. We never saw the velocity that he displayed in Double-A. Now, with the last couple of starts, we have. I just think that any player development that gets interrupted, you're talking about even arm speed that wasn't an issue because of his health."
Lester, who consistently showed a mid-90s fastball during his rise through the organization two years ago, is unbeaten in his last 11 starts in the Majors dating to Aug. 13, 2006, going 6-0 with a 5.55 ERA.
"You get back to baseball and now he's been able to throw with some consistency, his arm speed is really coming back," the manager said. "It takes a while, like strength. Things like that that when you compete like he does, you find a way to compete and it's nice to watch him compete with what he's accustomed to."
Routine workout: Manny Ramirez (left oblique) continued his work with rehab coordinator Scott Waugh Tuesday before taking some swings in the batting cage.
"He's in there right now with Scott Waugh doing his core work," Francona said. "I'm sure that will help him. I don't know if you can progress every day. I don't that with this injury, as long as there's still tenderness, I don't know if you can do that."
Stretching it out: While Kevin Cash caught Tim Wakefield on Tuesday, Doug Mirabelli (left hamstring) hopes to be back catching the knuckleballer the next time Wakefield takes the mound.
"He's doing better," Francona said. "I think his goal is to be ready for Wake's next start. That's probably realistic. We'll have to see where it goes."
Mirabelli aggravated his hamstring in his first start back last Thursday in Baltimore.
Rainy day duties: Tuesday's much-needed downpour wiped out a side session for Daisuke Matsuzaka and a Matt Clement session against hitters.
Clement will now throw his side session on Wednesday before facing hitters on Sunday.
"We've bumped Dice-K's side back to [Wednesday], so we'd have two pitchers with sides. Not a big deal," the manager added.
Tip of the cap: When Curt Schilling left Monday's game after six innings, he doffed his cap to home-plate umpire Chad Fairchild, a sure sign that the Sox pitcher felt his night was over.
"Sometimes even the unspoken helps guys compete," Francona said. "The way things had gone, we were going to take him out after that and he probably knew it. I didn't even watch to see if he looked at the umpire."
While Francona doesn't feel the need to go out and chat with his pitchers very often, Tampa Bay manager Joe Maddon was busy Monday night telling starter Scott Kazmir to treat his last two batters like he were in the playoffs.
"The only time I remember going out to the mound it was with Alex [Rodriguez] and he promptly walked him," Francona said. "So I stay the [heck] away. I don't need to [visit]."
Coming up: The Red Sox host the Rays in the finale of the three-game series at Fenway on Wednesday at 7:05 p.m. ET. Lester (4-0, 4.47 ERA) takes the hill for Boston while Tampa Bay, in their final Boston appearance this season, counters with right-hander Edwin Jackson (4-14, 6.00).
Mike Petraglia is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.