WHAT HAPPENED: Argentine Diego Schwartzman, the No. 20 seed, upset No. 6 Alexander Zverev of Germany, 3-6, 6-2, 6-4, 6-3, to advance to his second US Open quarterfinal.
Based on height differential alone, the fourth-round bout between the 5-foot-7 Schwartzman and 6-foot-6 Zverev looked to be a mismatch.
But the real mismatch may have been their road to this encounter. Zverev had played 14 sets in three tight matches, two of them tough five-setters against unseeded competition. The Argentine had cruised through his first three matches without dropping a set.
Over the course of four sets, under a closed roof on Ashe on a rainy Labor Day, Schwartzman demonstrated himself to be the fresher player, as well as the one with more confidence in his shots. The German was plagued by errors and a complete breakdown of his second serve.
A depleted Zverev double-faulted 17 times and had his serve broken on eight occasions by Schwartzman.
The tall German missed left and right, short and long. Early in the first set, Zverev hit a second serve at just 73 m.p.h. that bounced feebly on his own side of the court before even reaching the net. It was a serve more commonly seen at country clubs than the elite pro ranks.
Zverev had a whopping 65 unforced errors on the afternoon.
"I think today Alex had many problems with the serve," said Schwartzman. "But I think I played great tennis."
In a tight third set, with Zverev to stay in it at 4-5, 15-30, the German struck what appeared to be an ace. However, the call was challenged by Schwartzman and overruled. Zverev responded with his 14th double fault to give the Argentine double set point.
Schwartzman snatched the break and the set with the best point of the match. After a cat-and-mouse exchange at net, Schwartzman cracked a two-fisted backhand down the line for a winner. In the doubles alley, he raised his hands, exultantly, above his head.
The Argentine immediately broke serve and raced to a 3-0 lead in the final set, cruising to victory and the quarterfinals.
WHAT IT MEANS: Schwartzman's defeat of the world No. 6 equals his biggest previous win, in terms of rankings. The Argentine triumphed over then-No. 6 Kei Nishikori at this year's ATP Masters 1000 in Rome.
In his second appearance in the quarterfinals at Flushing Meadows, Schwartzman will face the winner of Rafael Nadal and Marin Cilic.
Zverev, who has been ranked as high as No. 3 in the world, has still only reached the quarterfinals at one of the four majors, the French Open.
MATCH POINT: Coming into this fourth-round match, Schwartzman was the only player remaining in the draw besides No. 2 Nadal who had yet to lose a set. Schwartzman has been ranked as high as No. 11 in the world.
Zverev, despite being firmly ensconced in the Top 10 for the past three years, has the lowest percentage of second-serve points won on tour, just 43 percent. Perhaps because of his serving woes, the German has played the most five-set matches of any player on tour over the past two years.
