CLEVELAND -- Thursday night, Mark Leiter Jr. was stuck watching the ALCS like the rest of us. Life comes at you fast.

Leiter was thrust into the biggest moment of the Yankees’ 8-6 win over the Guardians in Game 4 Friday night, the injury replacement for Ian Hamilton suddenly a pivotal piece of a bullpen that’s running on fumes. Thanks in part to his efforts, the Yankees now lead the series, three games to one, and sit one win away from the World Series.

An error of his own making brought in the tying run in the eighth, but Leiter was able to limit the damage after getting the Yankees out of the seventh with two of the biggest outs of the ballgame. This wasn’t manager Aaron Boone’s master plan, but given how hard he’s run this group recently, options were limited with one of Game 3’s heroes, Jhonkensy Noel, looming as a pinch-hitter for the Guardians in a massive spot.

“Well, we still had a long way to go to the finish line, and frankly I wasn't quite sure how we were going to get there,” Boone said after the win. “But I knew Noel was going to come in. I didn't necessarily think he would come in for Leiter, but I knew he would if I brought [Tim] Mayza in for that spot.”

Leiter got the news Friday morning that he’d be activated and Boone had a message for him. Perhaps it was foreshadowing. Be ready, Boone told Leiter, because you might just find yourself in the biggest moment of the game.

On Leiter's third pitch, with runners on first and second and one out, Noel -- who hit a dramatic game-tying home run in the ninth inning a night earlier -- lofted a deep fly ball to left field that Alex Verdugo ran down at the warning track. Leiter's ensuing strikeout of Andrés Giménez to end the seventh inning and strand the two Guardians runners stopped what felt like an avalanche of Cleveland momentum. Just 12 hours removed from finding out he was on the roster, there was Leiter, slamming his hand into his glove and screaming back to the dugout, a silenced crowd watching on at Progressive Field.

“It was definitely a good adrenaline rush,” Leiter said. “I tried, as much as possible, to keep it the same and stay in my routine. I just allowed my routine to work for me and treated it like another game. I really do feel like, as a late-inning reliever at times, you feel some of those moments and that energy. A lot of the time, you’re coming in when the crowd’s already going.”

It wasn’t perfect, though. With a runner on third and two outs in the eighth, a squibber back to the mound should have ended the inning, but Leiter booted it and after chasing the ball towards first base, delivered an awkward throw to Anthony Rizzo that slipped beneath his glove and through his legs. The stadium was shaking again.

“Just a little squibber that he knocked down and then kind of kicked,” Boone said, “so he still had a chance to make the play and got really close to Rizz -- so you kind of just handcuff, so it became wonky once he got over there. You have to secure it there on the first thing, but what an effort.”

Still, Leiter survived it. This is a bullpen group that needs help anywhere they can find it, and with Boone looking to avoid using closer Luke Weaver on Friday, the Yankees needed someone to step up.

• Yankees-Guardians ALCS Game 5 FAQ

“That was huge. That was the turning point of the game, Leiter coming in,” said Tommy Kahnle, who later closed it out. “He got those huge outs in the seventh, then went back out for the eighth and got us through. There was the error, but it’s baseball and that’s part of the game. His outing was absolutely tremendous. I think it was 100 percent one of the reasons we won this game.”

The “check engine” light is flashing on both of these bullpens. The Yankees eventually got to Emmanuel Clase -- again! -- to win the game in the ninth, another stunning turn for what was supposed to be the Guardians’ greatest strength. Cade Smith allowed the big blow of the game, too, a three-run shot to Giancarlo Stanton in the sixth to give the Yankees a 6-2 lead.

The Yankees knew they might run thin on the back end, but for the Guardians and their bullpen, this is a worst-case scenario.

“I mean, everybody is tired,” Guardians manager Stephen Vogt said. “I think we've used them a lot. We've had to. It's who we are.”

Welcome to October. The mighty Yankees, who won more games than any team in the American League, turned to a rookie starter in Luis Gil who hadn’t pitched in a game in 20 days. Then, when the game itself was about to erupt, Boone handed the ball to a reliever who hadn’t pitched in 19 days, one who woke up without a roster spot that same morning.

This wasn’t Plan A, but it doesn’t need to be. Plan A is to win, and in ways no one saw coming, Leiter and the Yankees are one win away from the World Series.