BOSTON -- The highest-scoring offense in baseball had been in a fall slumber for nearly two full games of the American League Championship Series, and the Astros were in danger of being pushed to the brink of elimination as a result.

The Astros had managed solo homers by Alex Bregman in the first inning and a game-tying shot by Jose Altuve in the eighth of Game 4 against the Red Sox on Tuesday night, giving themselves a fighting chance in a game that was tied entering the ninth at tension-filled Fenway Park.

A leadoff double in the ninth by Carlos Correa off Red Sox ace pitcher Nate Eovaldi -- who was working in relief -- set the stage for the Astros’ biggest playoff outburst in their history. Houston scored a team-playoff-record seven runs in the ninth -- all after two outs -- to stun the Red Sox and silence Fenway with a 9-2 win and tie the ALCS at two wins apiece.

“That was a huge win,” Astros manager Dusty Baker said. “To tie that up, to guarantee us to go back home and have some more games at home, so we got another big game [Wednesday].”

In all best-of-seven postseason series that have been tied after four games, the Game 5 winner has gone on to win the series 44 of 63 times (70 percent). Game 5 is set for Wednesday at Fenway Park.

• Wild stats from Astros' 7-run 9th in Game 4

“The last two games before this didn’t go the way that we wanted, but to finish this one tonight the way that we did was big for us,” said catcher Jason Castro, who broke a 2-2 tie with an RBI single in the ninth.

Correa’s double got things going, but he was still at second base with two outs when Castro came to the plate. He drilled a 2-2 pitch into right field to score Correa with the go-ahead run, and Michael Brantley came through with a bases-loaded double two batters later to send the Astros on their way to knotting up the series.

“That was a huge base hit by Castro to give us the lead, but we knew with this team that we're playing we wanted to pad the lead, and pad the lead we did,” Baker said. “That one run might not have stood up, especially in this ballpark.”

Castro entered the game as a pinch-hitter for starting catcher Martín Maldonado in the seventh inning and hit a screaming liner to first base for the final out before delivering in the clutch in the ninth.

“What impressed me the most was that he was sitting on the bench for seven innings on a cold night,” Correa said. “And you don’t have a batting cage nearby here to warm up or anything, because the ballpark is so old. I don’t know how he did it, but I admire that. I can tell you, I wouldn’t be able to do that. Sitting down for that long, and then facing guys that are throwing 100 in crunch time? That’s special.”

Castro, who endured three consecutive 100-loss seasons with the Astros from 2011-13 before leaving in free agency the year before Houston won the World Series in 2017, called it the biggest hit of his career.

“Probably, yeah,” he said with a laugh.

In the ninth, the Astros sent 12 batters to the plate and added on to their lead with two-out RBI hits from Yordan Alvarez, Correa and Kyle Tucker. Houston’s 36 two-out runs are the most by a team through eight games in a single postseason.

“I’m very happy that I could score with a homer right there and what we did in the ninth inning was amazing,” Altuve said. “Jason had a really good at-bat. It’s not easy to come off the bench and get two really good at-bats the way he did, and I’m just happy we won today.”

After Xander Bogaerts took Zack Greinke deep in the first to put Boston ahead, 2-1, Houston relievers threw 7 2/3 scoreless innings, led by three from Cristian Javier and two from Kendall Graveman. Somehow, the series is tied at 2 despite Astros starters throwing a total of 6 2/3 innings, with no starter completing the third inning. Houston’s bullpen has been clutch, though, posting a 3.49 ERA in 28 1/3 innings in the series.

• 'What a job': Astros' bullpen delivers in G4

“I'm just glad that we didn't quit,” Baker said. “What a job our bullpen did. Greinke just gave up that one hit [in 1 1/3 innings], and it was 2-1 for a long time. And then Javier, the job that he did, that was a great job. He just ran it. We took him as far as we could. He ran out of gas there and went to Graveman. You know, a great job by [Brooks] Raley. Just a great job overall by the whole team.”