BOSTON - This is Jon Lester unleashed: unhittable in May, a stopper in October, the emerging ace of the Boston Red Sox.

The 24-year-old lefty will start Game 3 of the AL championship series against Tampa Bay on Monday, facing Matt Garza at Fenway Park under the championship banner Lester helped raise with a World Series-clinching victory just months after he was cured of cancer.

“We're one of four teams left right now. You're playing for the ultimate prize. You're playing for another ring, a chance to be world champions again,” Lester said Sunday before Boston's off-day workout. “I think a lot of the young guys that were here last year get spoiled. We're doing it again. It's almost like we expect it, and this is all we know.”

All Lester has known lately is success - especially at Fenway.

He went 11-1 at home this season, including a May 19 no-hitter against Kansas City. He has not allowed an earned run in his last 22 2-3 postseason innings, including the Game 4 victory in the World Series as the Red Sox swept Colorado to win their second title in four seasons.

“He's pitching unbelievable right now, and I think he's become our ace,” Kevin Youkilis said. “Coming here at home he always pitches pretty well, so we've just got to have him pitch a good game and jump on Garza as soon as we can.”

The Red Sox took the opener of the best-of-seven series in Florida, but the Rays tied it Saturday night when B.J. Upton lofted a bases-loaded sacrifice fly to shallow right field in the 11th inning to give Tampa Bay a 9-8 victory. Josh Beckett, dominant in Boston's '07 title run, allowed eight runs in 4 1-3 innings, taxing the bullpen and leaving the Red Sox in need of a Game 3 rescue from Lester.