NEW YORK, July 23, 2023 (BSS/AFP) - Alex Michelsen's breakout run at the grass court tournament in Newport continued Saturday as the 18-year-old American toppled four-time champion John Isner 7-6 (8/6), 6-4 to reach his first ATP final.

Michelsen had never won a tour-level match until this week, but he arrived in Rhode Island brimming with confidence and with his ranking up to 190th in the world after claiming a first title on the low-level Challenger circuit in Chicago.

He saved a set point in the first-set tiebreaker, then pocketed the set two points later.

He broke Isner in the opening game of the second set and made the advantage stand up, finishing it off with style with back-to-back aces.

"I think I'm going to need a month," Michelsen said of getting to grips with the week.

"It's going to need a little bit for sure. It doesn't feel like I'm in the final, but that's probably a good thing. That's why I'm playing so loose."

Michelsen withstood 20 aces from his big-serving compatriot, who at 38 years old was giving away 20 years to the rising talent across the net.

"I knew he was going to serve two or three aces a game consistently, so I just focused on my serve to get to a breaker," Michelsen said.

"I got a little fortunate to win that first-set breaker and then I think I caught him sleeping a little bit (in the second) and then just held my serve."

Michelsen, who defeated defending champion Maxime Cressy in the first round, will play French second seed Adrian Mannarino for the title.

Mannarino defeated compatriot Ugo Humbert, the third seed, 6-4, 6-3.

Mannarino, 35, also reached the grass court final in Mallorca in June, falling to American Christopher Eubanks.

Michelsen, meanwhile, is in all-new territory.

He qualified at Mallorca to make his ATP debut in June, falling in his first match.

The teenager, who has yet to turn pro, showed no sign of nerves as the first set against Isner came down to the tiebreaker and saved all three break points he faced in the one hour, 42 minute clash.