NEW YORK — John Isner doubled over and rested his elbows on his knees. He grimaced. He shook his head.
He looked as if he wanted to be anywhere but where he was: Falling further and further behind against Juan Martin del Potro in muggy, energy-robbing heat at the US Open.
Isner’s bid to become the first American man in a dozen years to get to the final four at Flushing Meadows ended Tuesday with a 6-7 (5), 6-3, 7-6 (4), 6-2 loss in Arthur Ashe Stadium to No. 3 seed del Potro, the Argentine who won the 2009 championship.
The temperature, more than 90 degrees, made things uncomfortable across the 3½-hour match. So did the humidity, at about 50 percent. Those kinds of conditions were a problem for Roger Federer when he was upset by 55th-ranked John Millman a night earlier, and Isner had all kinds of trouble, too — certainly more than del Potro did.
Things got so bad around the site that the tournament suspended junior matches for a few hours in the afternoon. The U.S. Tennis Association invoked its new extreme heat policy, which allows men to take a 10-minute break after the third set, but that clearly didn’t help Isner, who quickly trailed 3-0 in the fourth.
This has been something of a breakthrough season at age 33 for Isner, including two hard-court titles and a run to his first Grand Slam semifinal, which happened at Wimbledon in July. He followed that up by getting to the quarterfinals in New York for the first time since 2011; no one from the U.S. has made it past this stage at this tournament since Andy Roddick in 2006, three years after he became the country’s most recent male champion at any major.
But del Potro presented all sorts of problems.
His serve is almost as imposing as Isner’s, while other elements of del Potro’s game — returns and, most notably, his thunderous forehand, which often clocks in at more than 100 mph — are superior.
And while Isner was playing before what could count as a home crowd, del Potro got all manner of support throughout, from the blue-and-white flags or soccer jerseys dotting the stands to the repeated singsong chants of his nickname, “delPo,” punctuated by clapping.
Those choruses resonated in the arena after key points, such as each time del Potro erased one of Isner’s break chances, three in all. Still, it was Isner who struck first, closing the opening tiebreaker with a 132 mph ace down the middle. That was the first set dropped by del Potro in the tournament.
He managed to take the next three, though, and now will face either defending champion and No. 1 seed Rafael Nadal or No. 9 Dominic Thiem in the semifinals on Friday. Nadal-Thiem was scheduled for later Tuesday night.
If Nadal wins that, he and del Potro would have a third consecutive Grand Slam meeting: del Potro lost to the 17-time major champ in the French Open semifinals and the Wimbledon quarterfinals.