HOUSTON -- Sidelined for the American League Championship Series, Astros ace Lance McCullers Jr. is heartbroken but trying to stay upbeat by helping the rest of his team in its matchup with the Red Sox.

"It's been a tough couple of days, but I can help lead this team in more ways than just pitching," McCullers said before Game 2 on Saturday. "Help the guys with the scouting reports, watching the game, trying to pick up on what I can. I can be there for them in more ways than one."

The Astros overcame a short start by Framber Valdez with a big performance by the bullpen and late homers by Jose Altuve and Carlos Correa in a 5-4 win in Game 1 on Friday night.

McCullers was left off Houston's ALCS roster because of a flexor pronator muscle strain in his right arm. He pitched 6⅔ scoreless innings in the Astros' 6-1 victory over the Chicago White Sox in Game 1 of their AL Division Series. He started again in Game 4 but departed after four innings with what the team called forearm tightness.

He said he felt something in his arm when he threw a slider to Gavin Sheets with two outs in the fourth in that game. McCullers was able to finish the inning, but knew something wasn't right after leaving the game.

McCullers was feeling better Saturday but still isn't able to throw. His availability for the World Series, should the Astros advance, is unclear.

"We're just going to have to see how I progress, see how I'm feeling over the next couple of days," he said. "We're fighting against time a little bit. I've got to be able to throw before I just pitch in a game. So today is a better day than yesterday was, and so hopefully those days keep adding up and we can see where I'm at."

McCullers, 28, signed a five-year, $85 million contract extension in March and then had the best season of his career.

He set career highs with 13 wins, a 3.16 ERA and 185 strikeouts to lead the rotation with Justin Verlander out all season after Tommy John surgery.

McCullers was placed on Houston's ALCS taxi squad so he can be in the dugout with the team and travel to Boston. Despite his efforts to help out in other ways, he is struggling with the fact that he won't be on the mound as the Astros try to reach their second World Series in three seasons.

"I want to be out there," he said. "I feel like in a way I've kind of let the guys down. I know I can't do anything about it, but it feels that way to me."