Lester, who tossed a no-hitter vs. the Royals on May 19, has arguably been the team's most reliable pitcher this season. He went 16-6 overall and was 4-1 in Boston's march through the stretch run of September.
There's no doubt he has the respect and the confidence of his teammates.
"We're going to be fine," Dustin Pedroia said. "Jon's throwing the ball great all season. We know what Josh can do in the postseason. We all saw it last year. It's an unfortunate thing, but he's going to be fine; he'll pitch Game 3 or whatever."
It was after Boston's Sunday night win over the Yankees that news swirled about Beckett's injury, something he suffered on one of his last pitches of a bullpen session on Friday. But manager Terry Francona said Beckett will play catch on Tuesday and throw another side session on Wednesday, hopefully putting himself in position to take the ball on Sunday at Fenway Park.
The severity isn't easy to gauge right now, Francona said, but the team will closely monitor how he responds to throwing over the next two days.
Beckett is 6-2 with a 1.73 ERA in the postseason. He's 2-0 lifetime in Division Series play, and, most impressively, no team with Beckett on its postseason roster has lost a series in general.
Such a blow to Beckett's health would be downright disheartening had it not been Lester's emergence as one of the American League's top pitchers in 2008.
"There's no getting around what Beckett has done during the postseason -- not only for us but for the Marlins [in 2003]," Francona said. "I think we're all looking forward to Jon Lester maybe making his time. This is an exciting time."
Lester was largely speculated to be the Game 2 starter on Friday anyway, making this transition not terribly drastic. As Mike Lowell pointed out, Lester was slated to pitch two of the five games in this ALDS anyway, if necessary.
That makes this just a one-game adjustment, with 18-game winner Daisuke Matsuzaka taking the hill in Game 2 instead. Though Dice-K is often criticized for allowing too many walks while not logging a ton of innings, he also won 15 more games than he lost in 2008.
In the process, he went 9-0 on the road this season with a 2.37 ERA in 13 starts -- a stint in which hitters batted just .178 against him.
"You want Josh Beckett to go for you, but the alternative of having Jon Lester and Dice-K going for you isn't too bad, either," said Kevin Youkilis. "We've got three great pitchers, for all of us position players we don't mind them out there. We'll take them out on the mound."
It all starts with Lester, who is 4-0 with a 1.68 ERA in five starts against teams who have already qualified for the 2008 postseason -- including the Angels, Rays and Phillies.
No question he's been starter the Sox have turned to throughout the season when they needed a crucial win.
They'll do it again on Wednesday.
"We love what Beckett can do -- we respect what Beckett can do," Francona said. "I think we're starting to get the same feeling about Lester."