NEW YORK – Trying to extend his stay at the U.S. Open, John Isner smacked a return winner, then pointed his right index finger toward the Louis Armstrong Stadium stands and circled his arm overhead, riling up the fans.

Two points later, sprinting so far he nearly reached the seats, Isner hit a forehand that closed a point, punched the air and then shook his fists, doing his best Jimmy Connors imitation. Minutes after that, Isner cupped his hand to his ear, basking in the chants of “U-S-A! U-S-A!”

The highest-ranked American man finally heard the adulation he’d been hoping for a couple days earlier, when he lamented that so many spectators cheered so vociferously for his French opponent. What the 13th-seeded Isner failed to do in return Saturday was deliver a victory in the third round at Flushing Meadows, meaning only one U.S. man remains of the 15 in the field.

Isner even blamed those exuberant attempts to stir the crowd for his struggles down the stretch of a 6-4, 3-6, 7-5, 7-6 (5) loss to 22nd-seeded Philipp Kohlschreiber of Germany.

“I felt like I wore myself out getting charged up out there,” Isner said after bowing out against Kohlschreiber in New York for the second consecutive year. “I used too much energy, and I shouldn’t have done that. It was stupid on my part. So I was pretty gassed there.”

No such concerns about getting tired for Roger Federer. The 17-time Grand Slam champion worked quickly once again, beating 63rd-ranked Adrian Mannarino of France 6-3, 6-0, 6-2 in 1 hour, 21 minutes to get to the fourth round for the 13th consecutive year. Through three matches, Federer has dropped 21 games and spent a total of 4½ hours on court.

Next for Federer is 19th-seeded Tommy Robredo of Spain, who ended the run of 179th-ranked qualifier Daniel Evans of Britain 7-6 (6), 6-1, 4-6, 7-5. Win that, and Federer could face 12-time major champion Rafael Nadal in the quarterfinals; the two rivals never have played each other in New York.

The other American man in action Saturday, 20-year-old Jack Sock, was beaten 3-6, 7-6 (1), 6-1, 6-2 by No. 18 Janko Tipsarevic of Serbia.

So the last man from the United States left is Tim Smyczek, a 25-year-old from Milwaukee who got into the main draw thanks to a wild-card invitation and plays 43rd-ranked Marcel Granollers of Spain on Sunday. If Smyczek loses — a distinct possibility, considering he’s ranked 109th and never before made it past the second round at Grand Slam tournament — it would be the first time with no U.S. men in the round of 16 at the U.S. Open, which was first played in 1881.

“I don’t care,” said Isner, who double-faulted to get broken in the last game of the third set, then was broken again while serving for the fourth. “I’m going to watch football for a while. That’s all I care about.”

A loss by Smyczek also would make 2013 the first year with no Americans in the second week of any of the four majors.

Even if Smyczek wins, it still would be only the second time there was just one American in the fourth round at the U.S. Open. The other? In 2009, when Isner was the lone one in the second week.

All part of the recent decline of American men’s tennis.

“Well, what shall I say? I think, yeah, it’s bad luck,” said Kohlschreiber, whose next opponent is 12-time major champion Rafael Nadal, a straight-set winner Saturday. “For sure, it’s not great for the American history not to have a player in the second week. But you had so many good years.”

There’s a trio of Americans in the women’s fourth round, because wild-card entry Alison Riske, ranked only 81st, eliminated 2011 Wimbledon champion Petra Kvitova 6-3, 6-0. The seventh-seeded Kvitova got her blood pressure checked by a trainer, then said afterward she had a virus and a fever.

There’s no doubt the other two U.S. women who are left belong: No. 1 Serena Williams and No. 15 Sloane Stephens play each other Sunday with a quarterfinal berth on the line. Williams is seeking a fifth U.S. Open title and 17th Grand Slam singles trophy. Stephens is one of only three women to reach the round of 16 at every major this year, and she beat Williams en route to the Australian Open semifinals.

Italy’s Camila Giorgi pulled off the day’s biggest upset. The 136th-ranked Giorgi defeated sixth-seeded Caroline Wozniacki, 4-6, 6-4, 6-3.