NEW YORK -- Once upon a time, Trevor Stephan would have dreamed of taking the mound at Yankee Stadium with the Yankees holding a lead.

Three years ago, he was the Yankees’ No. 8 prospect according to MLB Pipeline, a third-round Draft pick out of Arkansas who overpowered Class A hitters and seemed on a fast track. How he ended up on the other side is an interesting journey.

Still, as he took the mound for the sixth inning Tuesday in Game 1 of the American League Division Series, he was only thinking about keeping the Guardians within striking distance.

“It was a cool moment, I guess,” he said Wednesday. “Obviously warming up in that situation, I wish I came into the game with a closer game, but I thought Cal [Quantrill] pitched his tail off.”

The inning showed why Stephan has become so vital to Cleveland’s relief corps. After retiring Gleyber Torres and Giancarlo Stanton on sliders, Stephan escaped a 3-0 count against rookie Oswaldo Cabrera by challenging him with fastballs. After Cabrera fouled off a 98 mph heater, Stephan unleashed a nasty splitter that fanned him.

“He’s continued to be aggressive and trust himself in big situations this entire year,” Shane Bieber said. “He’s come a long way in a year, and I think he’s going to continue to grow.”

The Yankees had a loaded pitching staff at Double-A Trenton in 2019. Of the 30 pitchers who appeared with the team that season, 19 have made the big leagues. While future Yankees Deivi Garcia, Clarke Schmidt and Michael King were there, so were future A’s closer Domingo Acevedo and current Red Sox hurler Garrett Whitlock. So was Stephan, then a struggling starter.

Three pitchers, including Whitlock and Stephan, ended up going to other organizations in the Rule 5 Draft in 2020. Though Stephan posted a 5.24 ERA in 12 starts for Trenton, the Guardians saw something.

“I was happy, honestly,” Stephan said. “In 2020, I was at home. I didn’t get invited to the alternate site. After that happened, I was hoping I’d get Rule 5-ed. To get this opportunity with Cleveland, it was a blessing.”

Stephan pitched in 43 games last season, mostly lower-leverage appearances. He gave up 15 home runs in 63 1/3 innings, but racked up 75 strikeouts. His 96-98 mph fastball played bigger with his arm extension.

For many Rule 5 picks, the next season often includes a return to the Minors to build off lessons learned in the big leagues. Not only did Stephan stick in Cleveland, he found a bigger role.

“We actually, early in the season, put him in some pretty high-leverage situations, just because we were really young,” manager Terry Francona said. “And even though it was a shortened Spring Training, he was throwing the ball really well.”

He was also throwing differently. While he was almost exclusively a fastball-slider pitcher last season, he mixed in a splitter as a change of pace that was raising eyebrows.

“I saw it when we first got him two Spring Trainings ago,” Bieber said. “In his first live [batting practice] he was throwing a splitter. I was like, ‘Oh, that’s real.’”

A year later, it was even better.

“It was the same pitch, but it definitely developed,” Stephan said. “I threw it more around the strike zone, and it became more of a weapon to lefties and righties. I never had that in the Minors or the first half of my rookie year.”

While veteran Bryan Shaw taught him the grip, former teammate Blake Parker taught him how to use it. The result was a game-changer, which according to one rival evaluator made at-bats against him far more uncomfortable. Right-handed hitters, who slugged 11 homers off him last year, hit just one this season, batting .207 with 45 strikeouts in 153 plate appearances. Lefties also hit him with less power than last year.

“The split early in the season helped a ton, especially against left-handers,” Francona said. “Then I think, like a lot of people, he kind of fell in love with it, and then he kind of lost it a little bit. But he's come back, like good players do.”

The metrics on Stephan are stellar. He ranked among the top Major Leaguers this season in strikeout rate (90th percentile), swing-and-miss rate (96th), barrel rate (98th), expected batting average (91st), expected slugging percentage (97th) and fastball spin rate (95th). The spin rate is particularly impressive, with an average velocity in the 89th percentile and arm extension in the 70th percentile. His chase rate is in the 88th percentile.

No wonder Stephan joined a rejuvenated James Karinchak and All-Star closer Emmanuel Clase to form a dominant late-inning trio. The next time he pitches against his old club, he could have a chance to beat them.

“This kid was Rule 5’ed a couple years ago, and now he’s pitching a lot of games in the eighth inning,” Francona said. “That’s pretty impressive.”