BOSTON -- An unlikely source jolted late life into the Houston Astros' offense and helped level the American League Championship Series.

After being stifled for the better part of three games, the Astros came alive in a seven-run ninth inning to rally past the Boston Red Sox for a 9-2 win on Tuesday night, evening the best-of-seven series at two games apiece.

They have backup catcher Jason Castro to thank for it.

Castro's two-out single to right-center field off Red Sox pitcher Nathan Eovaldi (1-1) plated Carlos Correa to make it 3-2.

"It just fell on my spot in the order to come up, so glad I was able to push that across," said Castro, who entered the game as a seventh-inning pinch hitter. "To see what we did after that, that was a nice swing of momentum for us."

After Jose Altuve walked, Martin Perez replaced Eovaldi and immediately surrendered a two-run double to Michael Brantley. Yordan Alvarez, Correa and Kyle Tucker tacked on RBI singles to cap Houston's rally.

"We know where we're at," Red Sox manager Alex Cora said. "I think it was a good game until the end, right? We were one pitch away from ending that inning, and it didn't happen, and then they scored seven."

Houston reliever Kendall Graveman (1-0) picked up the win after tossing two scoreless innings. Eovaldi was charged with four runs in two-thirds of an inning.

"Tonight we had to battle," Eovaldi said. "We had to work. We were in the game all the way up until the ninth inning."

Altuve hit a tying solo blast into the Green Monster seats in left to make it 2-2 to open the eighth. The homer was Altuve's 21st in postseason play, breaking a tie with Hall of Famer Derek Jeter for the third most in baseball history.

"Every time you hit a homer, you're scoring some runs for your team -- and we're trying to win," Altuve said. "In order to win, you need to score some runs. I'm happy that I'm hitting those homers."

Alex Bregman added a solo homer for the Astros, who had been outscored 21-8 in back-to-back losses in the series. The Red Sox were 12-3 winners in Game 3 at home on Monday after registering a 9-5 win in Game 2 on Saturday in Houston. The Astros took the series opener 5-4 on Friday.

Game 5 is Wednesday evening in Boston.

"All I know is we've got to go back out there (Wednesday) and play clean baseball again," said Astros shortstop Carlos Correa, who went 2-for-5. "Man, it was just a beautiful game (on Tuesday)."

After falling behind 9-0 in back-to-back games, the Astros struck first as Bregman sent Boston starter Nick Pivetta's ninth pitch of the game into the Green Monster seats in left field for a solo blast.

Houston's momentum didn't last for long as Boston's Xander Bogaerts retaliated by taking Astros starter Zack Greinke deep over the Green Monster for a two-run homer in the bottom of the first.

Bogaerts' homer was Boston's 21st of the 2021 postseason, a single-season franchise record. It was the third homer of this year's playoffs for the All-Star shortstop, who had two of the Red Sox's five hits.

Pivetta tossed five innings of one-run, two-hit ball while Greinke allowed two runs on one hit and three walks in 1 1/3 innings.

"I don't think (this loss) is going to affect us at all," Pivetta said. "I don't expect us to really take too much from it. Just move on."

--Gethin Coolbaugh, Field Level Media