Another early exit for Isner

John Isner had a chance to make the Round of 16 and set up an All- American bout against Sam Querrey on Labor Day weekend.

Instead, Mischa Zverev, the lesser-touted Zverev brother, ruined the party with an artistic serve-and-volley game, posting a 6-4, 6-3, 7-6 victory over the 10th-seeded Isner on Friday night.

Mischa, seeded 23rd, will face Querrey on Sunday while his fourth-seeded brother Alexander is long gone — ousted in the second round.

“Everyone was expecting [Alexander] to be here in the Round of 16, but now it’s me,’’ Mischa said. “My next opponent is another American and playing unbelievable tennis.”

If the 6-foot-10 Isner couldn’t make a big run at this year’s decimated Open, with his favorable draw, he probably never will.

“I struggle playing at night at this tournament,’’ Isner said. “It sucks.’’

The left-handed Zverev plays a style that has become a lost art. His spin serve and lovely chip volleys are reminiscent of John McEnroe and he’s shown how effective it still can be when ousting Andy Murray in the Australian Open.

“I couldn’t pass him — that’s what it comes down to,’’ Isner said.

Isner also battled a sore neck. At 3-3 in the second set, Isner, while serving, was broken after committing two straight double faults. A medical timeout ensued as the American got treated for an neck problem. The trainer did all sorts of massage therapy, seemingly twisting Isner’s neck every which way during the fourminute session.

Nothing worked and Zverev chipped his way to the fourth round. It was déjà vu for Isner, who was beaten by another German, Philipp Kohlschreiber three straight years at the Open.

Roger Federer is making the practice rounds. After holding an impromptu session at Central Park on Wednesday, the Swiss maestro took his crew to Randall’s Island to hit at the Sportime facility, home of the John McEnroe Tennis Academy. The 2014 Open champ

Marin Cilic missed his big chance for another title, also failing to take advantage of being on the decimated side of the draw. The fifthseeded, Croatian was knocked out Friday in a shocking loss to 29th-seeded

Diego Schwartzman, 4-6, 7-5, 7-5, 6-4, on the Grandstand. Cilic has battled an abductor ailment.