BOSTON -- Six outs away from putting the Astros in a stranglehold in this American League Championship Series, the Red Sox instead saw the tables turned on them in the late innings and suffered a painful 9-2 defeat in Game 4 on Tuesday night at Fenway Park.

On a night the Boston bats -- which had been producing at a historic rate in this postseason -- at last cooled off, Red Sox manager Alex Cora put the late innings in the hands of the two best pitchers on his staff this season in Garrett Whitlock and Nathan Eovaldi.

It didn't work.

Suddenly, the ALCS is knotted at 2-2, turning it into a best-of-three series. Game 5 is Wednesday, with Chris Sale on the mound for Boston. It is the final game at Fenway before the series shifts back to Houston for Game 6 and 7 (if necessary).

"There's not much to say in that clubhouse," said Cora. "We know where we're at. They have a good team. We were one pitch away from ending that [ninth] inning and it didn't happen, and then they scored seven. Just like every day, you win, you turn the page. You lose, you turn the page and be ready."

The Red Sox had led, 2-1, from the time Xander Bogaerts belted a two-run homer over everything in left in the first inning until the first pitch of the eighth inning.

And that was when Whitlock, Boston's best reliever all season, served up a game-tying solo homer to Jose Altuve that changed the momentum of the night.

"He just hit a first-pitch fastball out," Whitlock said. "I was trying to get ahead and throw strikes, so tip my cap to him."

With the game tied in the top of the ninth inning, Cora went with ace starter Eovaldi in relief. Though it was the first time Eovaldi pitched out of the bullpen this season, this has been a frequent route taken by Cora in this postseason and when Boston won the World Series three years ago, using starters as rovers.

One pitch away from getting out of the ninth inning with the game still tied, Eovaldi gave up a line-drive single to Jason Castro that put the Astros in front. Eovaldi thought he had Castro on a 1-2 curveball and started to trot off the mound.

But home-plate umpire Laz Diaz, who had an inconsistent night, called the borderline pitch a ball. According to Statcast and television replays, it looked like it grabbed the upper outer portion of the strike zone.

"I thought it was a strike, but, again, I'm in the moment," said Eovaldi. "I'm trying to make my pitches. I'm attacking the zone."

From there, Eovaldi tried to regroup. Castro fouled a 97.6 mph heater straight back. The next pitch was a splitter and Castro got enough of it to find a patch of grass in center, sending a surge of noise into the Houston dugout and a mixture of groans and silence throughout the crowd of 38,010 at Fenway.

"I felt like I made a good pitch on the outside corner, and it didn't go my way, but I've got to come back and I've got to answer back and make another good pitch," said Eovaldi. "I threw a fastball, and he fouled it off, and I went with the splitter. I had a good feel for it tonight, and he put a good swing on it and got a base hit."

Cora used Eovaldi exactly how he planned, allowing him to live with the result.

"He was going to give us one inning and we felt right there in that pocket it was good for him," Cora said. "I wasn't going to use him in extra innings, because then I get tempted to use him for six. So I decided to use him in the ninth and it didn't work."

From there, the Astros piled on -- against Eovaldi and low-leverage lefty Martín Pérez. Eovaldi was lifted after 24 pitches and is still on track to start Game 6 on Friday at Minute Maid Park.

In the first postseason start of his career, Nick Pivetta fired five strong innings, allowing two hits and a run. The righty departed with a 2-1 lead.

If Cora's decision to pull Pivetta after just 65 pitches seemed questionable, he had some data to back it up.

In the sixth inning of his starts this season, Pivetta had a 6.94 ERA, by far his worst of any inning. Also, on pitches 76-90, hitters had a 1.036 OPS against him.

The Astros were also making their third trip through the order, which is a non-starter for many managers in this era of playoff baseball. Again, Cora had the numbers to back up the decision. In Pivetta's third time through the order this season, opponents had a 1.011 OPS against him.

"I think it's always tense in the postseason," said Pivetta. "It's my first start, first experience like that, so it was very interesting."

And after a jarring turn of events for the Red Sox, this ALCS has again gotten very interesting as well.