Already down 2-0 to their hated rivals, the New York Yankees, the Boston Red Sox learned Thursday that Curt Schilling is definitely a scratch for Game 5 of the American League Championship Series and could possibly miss the remainder of the postseason with a torn tendon in his right ankle.

Schilling, who won a league-high 21 games during the regular season, was scheduled to participate in a bullpen session during the team's workout at Fenway Park, but the ankle was too sore to allow him to throw. Without enough time to prepare, the Red Sox pulled Schilling from Sunday's start. Derek Lowe, 14-12 with a 5.42 ERA during the regular season, is scheduled to take his place if there is a Game 5.

"It's not over," Boston Manager Terry Francona said of Schilling's chances of throwing again in this series. "He's going to continue to try to prepare. But as far as Sunday goes, he's not starting."

Schilling arrived at Fenway Park wearing a heavy boot on his right foot. He was in the clubhouse for a few moments, then left without speaking to reporters. But Schilling, who has made connections with Red Sox fans by calling radio stations and chatting on fan Web sites since arriving in Boston this offseason, called Boston radio station WEEI to comment.

"I tore this thing facing Miguel Cairo, the last out of the Yankee game during the regular season," Schilling said. "And it popped on the first pitch thrown to him and there was some pain. I threw five more pitches I think to finish that game, and I was out of the game after that."

Schilling said he felt pain during his Game 1 win in the division series against Anaheim. At one point during that start, Schilling, on his way to the dugout, grabbed his ankle and winced in pain.

"The most serious days were the days following that where I had an appreciable amount of swelling and a lot of tenderness and a lot of discomfort," Schilling told the radio station. "The Red Sox talked to everybody they could to address the issue. The two days leading up to the game against the Yankees were by far the two best days I've had up to this point. I was going into that game incredibly confident that whatever we were dealing with, we were going to be able to overcome. And then I had problems in the bullpen."

So the Red Sox, a team built around aces Schilling and Game 2 loser Pedro Martinez, turn to Branson Arroyo for Friday's pivotal Game 3 at Fenway. A waiver-wire pickup by the Red Sox prior to the 2003 season who has pitched at the back end of Boston's rotation all this season, Arroyo comes to the forefront with Boston's flickering pennant hopes on his shoulders.

Though he pitched well at the end of the year, going undefeated in September, Arroyo (10-9, 4.03 during the regular season) has started just one postseason game, getting a no-decision in Game 3 of the division series against the Angels despite yielding just three hits and two runs.

Prior to this season Arroyo, 27, never had started more than 13 games in a season and had failed miserably in three stints with the pitching-poor Pittsburgh Pirates, who in February of last season put him on waivers. He was claimed by the Red Sox.

"I don't feel the weight of the entire season," Arroyo said. "I obviously feel a lot of pressure from this series. But, you know, we're not down 3-0 in the ALCS. But obviously we're backed into a corner and there's going to be a huge, huge game."

Arroyo, named for the actor Charles Bronson, began the season in the bullpen, losing the fifth starter spot to Byung Hyun Kim. By the end of the season, Arroyo had surpassed Kim and even Lowe and Tim Wakefield in the playoff rotation. If he hadn't already received enough attention, Arroyo twisted his blond locks into corn-rows, becoming something of a tall, white, blond-haired version of Allen Iverson.

Asked to explain Arroyo's hairstyle, Boston pitching coach Dave Wallace said: "He plays the guitar and he's from Key West [Fla.]. Come on."

Arroyo -- on a squad boasting several players in bands, including General Manager Theo Epstein -- is the team's most accomplished guitarist. He performed in a team charity concert last winter, singing a solo version of Pearl Jam's "Black" that wowed the crowd.

Arroyo, one of the quieter members of the otherwise loud Boston clubhouse, delivered a pitch-perfect rendition of the song, by almost all accounts, including a chorus that involves a screaming roar.

Arroyo will need to provide the same type of performance Friday. The rivalry, the much-anticipated rematch from last year's momentous ALCS, is one Yankees win in Game 3 from becoming an overrated romp.

"I think [Schilling is] one of the biggest, if not the biggest addition to this team this offseason," Arroyo said. "If he can't go the rest of the series, I definitely think it's hurting us. Any way you look at it, guys can step up, Derek Lowe, Tim Wakefield, whoever can take the mound and throw an unbelievable game and we can win, regardless."

The Red Sox insist they aren't doomed by Schilling's injury. With Arroyo, Wakefield and Lowe they have three starters who have proven success in the regular season. They also are encouraged by a return to Fenway Park, where they had the second-best home record in the majors in 2004. But Lowe has thrown just one inning since Oct. 3. Wakefield, Boston's starter in Game 4, has thrown just one inning since Oct. 1. Certainly the Red Sox had put most of their hopes on Schilling.

"He's one man," Johnny Damon said. "It doesn't weigh on our minds. There's not much that weighs on our mind. We're not too smart."

Red Sox starter Curt Schilling, left, is out with ankle tendon tear, so Pedro Martinez, Game 2 loser, will have to pick up the slack.