Alexander Zverev was not at his flying best on Tuesday afternoon inside Arthur Ashe Stadium, but he still found a way to win.

The fifth seed rallied past long-time rival Borna Coric 1-6, 7-6(6), 7-6(1), 6-3 to reach his first US Open semi-final. Zverev had lost all three of his previous tour-level tie-breaks against Coric, but his calm under pressure proved vital in their quarter-final at the USTA Billie Jean King National Tennis Center.

"I just started playing maybe a little bit more aggressive because if I would have played the way I played, that's not the level for a quarter-final match of a Grand Slam," Zverev said. "I had to start playing better and I was a little bit more consistent then as well. My serve got better and I thought to myself, 'I'm down 6-1, 4-2, I have nothing to lose.'"

Coric has been Zverev’s kryptonite dating back to their junior days. The Croatian beat the German in the 2013 US Open boys’ singles semi-finals and entered this match leading their ATP Head2Head series 3-1, including a four-set victory in New York three years ago. But Zverev did a better job of reducing his errors when he needed to, triumphing after three hours and 24 minutes.

The 2018 Nitto ATP Finals champion is the first German US Open semi-finalist since Boris Becker in 1995. The highest-ranked seed remaining in the top half of the draw will play 12th seed Denis Shapovalov or 20th seed Pablo Carreno Busta for a spot in his first major final.

It was like déjà vû for Zverev, who lost the first set of his Australian Open quarter-final earlier this year against three-time major winner Stan Wawrinka 1-6, before rallying to beat the Swiss in four sets. On this occasion, Coric led by a set and a break, but he was unable to put away the fifth seed.

The 27th seed was two service holds from taking a two-set lead, but Zverev curled a cross-court forehand passing shot for a winner to get back on serve. The German spent a large portion of the match behind the baseline. But from that moment, Zverev reduced his errors, forcing the Croatian to beat him, which he did not.

"At some point I told myself, 'Look, if you keep playing like this, you're going to be down two sets to love in a blink,'" Zverev said. "I needed to be more aggressive, needed to go into the rallies and be more stable as well. At the end of the day, this is what I did and this is why it worked out for me."

In three of the final four points of the second-set tie-break, Coric had short balls to hammer away, but he missed them all. Zverev let out a loud roar after the Croatian missed a backhand into the net to end the set, and he progressively increased his level from there.

Zverev faced a dangerous moment at 5-6 in the third set, when he quickly rushed for a short ball to avoid facing two set points, ultimately cruising through the day's second tie-break. 

Zverev closed out the match with a big first serve, immediately turning around towards his camp and cracking a smile. The 23-year-old crushed 18 aces and won 76 per cent of his first-serve points. He hit 52 winners to 46 unforced errors.

"It was a very good match, very good competing, as well. In the third and fourth sets, I just felt like he also raised his level," Coric said. "He was playing some really, really good tennis, because I thought I was not actually playing bad. I just thought he was too good in the third and in the fourth sets."