WHAT HAPPENED: In a four-hour classic on Saturday night that finished after 2:20 a.m., No. 7 seed Marin Cilic continued his five-set success at the US Open by rallying from two sets down to outlast #NextGenATP Aussie Alex de Minaur, 4-6, 3-6, 6-3, 6-4, 7-5, in Louis Armstrong Stadium.

“It was just an insane atmosphere. [De Minaur] has an incredible fighting spirit... He played some insane tennis and I was just a little bit luckier today,” said Cilic in his on-court interview. “I’ve played a few matches in my career in the night sessions, [but] this is a moment to remember.”

The 19-year-old de Minaur was in uncharted territory at the US Open, having never won a main draw match in New York prior to this week, but he appeared unfazed by the moment. Leaping into his backhand returns and displaying a brand of counterpunching tennis similar to fellow Aussie Lleyton Hewitt, he showed a willingness to gamble on his shots that paid dividends. Serving for the opening set at 5-4, a beautiful backhand pass on the run earned a standing ovation from the crowd, and the Aussie eventually closed out the set with an ace.

But while de Minaur was on song in the early stages of the match, Cilic was out of sorts. The 2014 US Open champion hit 15 winners to 34 errors in the first two sets and struggled to find the range on his forehand. Cilic’s serve is normally his biggest weapon, but he dropped five of his 10 service games in the first two sets. Fittingly, a double fault down set point at 3-5 gave de Minaur a commanding two-set lead.

It appeared the teenager was well on his way to a massive upset, but Cilic raised his level considerably for the third set. Adding more weight to his shots and showing an ability to play defense when needed, he broke de Minaur early to lead 2-1 and then secured an additional break to grab the set.

As the match wore on, the court coverage required from de Minaur to stay in rallies began to see the momentum shift. While Cilic continued to hold comfortably, the young Aussie was pushed to the limit in his service games. De Minaur bravely saved five break points at 3-4, but then faced a pair of set points on his serve at 4-5. On the second set point, an ill-advised drop shot saw Cilic punish a backhand and bring the match to a decider.

Both men traded early breaks to start the match, but de Minaur’s frustration at squandering a two-set lead began to boil over. After missing a break point chance at 2-2, the normally composed Aussie cracked his racket in frustration and was eventually broken himself in the next game.

It appeared that victory was inevitable for the Croatian, but de Minaur brought the crowd to their feet by saving five match points on his serve at 2-5, including one with an around-the-post backhand. Cilic earned a sixth match point on his serve in the next game, but the Aussie leaned into a backhand return to erase it. Buoyed by the energy of a hardcore Armstrong crowd that stayed well after 2:00am, de Minaur shockingly broke Cilic and roared his approval, eventually leveling the final set at 5-5.

However, it would be the last push in a truly admirable fight from the Aussie. De Minaur was forced to stare down three more match points at 5-6 and managed to save one, but a forehand winner from Cilic on his eighth match point closed out the contest after exactly four hours of play.

WHAT IT MEANS: With this win, Cilic scores the sixth victory of his career from two sets down. He also improves to 8-1 in five-set matches at the US Open.

Next up for Cilic is No. 10 seed David Goffin. Although Goffin leads their head-to-head 3-2, Cilic has won their last two matches.

Despite the loss, de Minaur can take solace in the fact that he will move into the Top 40 of the ATP rankings when this tournament is over.

MATCH POINT: The US Open is Cilic’s most successful Grand Slam, with a 32-8 (80 percent) record after tonight.