Most tennis players would celebrate a victory over Rafael Nadal with a steak or some champagne, maybe a glass of nice wine and a plate of pasta. David Ferrer devoured a Big Mac at McDonald’s.

The wiry Spaniard with the tireless legs and wicked forehand skipped into the semifinals of the U.S. Open yesterday with a 6–2, 6–3, 7–5 victory over Juan Ignacio Chela. Ferrer looked fresh despite having traded blows with Nadal for three and a half hours on Tuesday evening and into Wednesday morning. Their match ended at 1:50 a.m., and Nadal, the ultimate, albeit banged up, practitioner of tireless tennis, was left sitting on the court in pain as Ferrer bounced along the baseline like a man who had just consumed five cups of coffee. By the time he returned to his hotel, it was 4 a.m.

“My coach and me walked into the McDonald’s,” Ferrer said. “Only thing open 24 hours. I’m very hungry.”

Ferrer, 25, will play in his first Grand Slam semifinal on Saturday. He got there with a clean, and quick, performance against Chela, an Argentine whose defense was no match for Ferrer’s superior retrieving skills and surprising offense. The Spaniard punctuated the win with a second-serve ace on match point.

Ferrer’s serve ended the match, but his returns have carried him to the best season of his career. He leads every return category tracked by the tour: points won returning first serves (35%), points won returning second serves (58%), break points converted (49%), and return games won (38%). No other player rates in the top three in all four of those categories.

No other player has beaten Rafael Nadal by outrunning him, either. Even though Nadal’s knees were not right this tournament, Ferrer’s effort was remarkable considering the setting — a late start at Arthur Ashe Stadium, following Serena Williams and Justine Henin — his mediocre results at the U.S. Open before this year (4–4), and the fact that he had played for four hours in his previous match against David Nalbandian, who missed a backhand, his best shot, on match point in the fifth set before Ferrer stole the contest.

Ferrer lost the first set against Nadal and the first two games of the second set. That’s a difficult deficit to overcome against most players, never mind the most intimidating physical specimen on the tour. Roger Federer, speaking after his latest victory over Andy Roddick, said it was sad to watch Nadal “fighting with his body” in that match, but credited Ferrer for pushing Nadal to his breaking point.

“He played unbelievable,” Federer said. “He’s the best returner in the game at the moment, together with Nadal I think.”

“Roger said this?” Ferrer asked yesterday. “Thanks, Roger.”

Ferrer is only 5 feet 9 inches and 160 pounds, and he looks like one of those people who wouldn’t gain an ounce if he ate five or six Big Macs a day. He burned so much fuel against Nadal, bouncing a dozen times before every service return and sprinting after every shot, that it’s a wonder he didn’t collapse from exhaustion. Perhaps caffeine keeps him going. Or maybe he has given up the cigarettes he smoked during a Davis Cup match in North Carolina earlier this year, according to a local columnist (Ferrer was injured and could not participate in the tie against America). Rafael Nadal losing to a man who smokes and eats Big Macs? Who would have imagined that when this tournament began?

Ferrer is further proof that there are no national or surface barriers in men’s tennis these days. Countries that traditionally produced clay court experts are now just as likely to develop players who perform well on the game’s faster surfaces. Ferrer and Chela benefited from a soft patch in the draw, but one can’t say that either of them was a fluke quarterfinalist. The same goes for Carlos Moya, the former French Open champion who has played his best tennis in years this season despite turning 30.

Though Ferrer says he’s not playing any different on hard courts than he would on clay, he’s not playing an entirely defensive game. Ferrer won’t ever be accused of volleying like John McEnroe, who demonstrated his technique on the practice courts yesterday in a light hit with Jim Courier, but he’s adept at the net and runs so fast that he can sneak in when he realizes that his opponent will send back a return with little pace. In doubles this summer, Ferrer and his partner, Nicolas Almagro, nearly beat Federer and his occasional doubles partner, Yves Allegro. Ferrer and another partner, Albert Montanes, played the top doubles pairing of Mahesh Bhupathi and Nenad Zimonjic to two tiebreakers in New Haven, Conn., the week before the Open began. For a man of Ferrer’s size and pedigree, that’s no small feat.

Many in tennis complain that balls are heavier these days and surfaces slower, but little data exists on the subject. The players insist this is true; Ferrer, who prefers clay courts, agreed yesterday. Yet it seems just as likely, and perhaps more likely, that men who normally win clay matches because of speed and stamina have learned to use their quickness on hard courts, and also learned to take more chances when opportunities arise. As impressive as Ferrer’s feet were against Nalbandian and Nadal, his ability to hit winners — hard and routinely on lines — was more so.

Is Ferrer playing well enough to reach the final? Definitely. We’ll assume that Moya and Novak Djokovic, the no. 3 seed, had a difficult match last night. Djokovic, many people’s pick to reach the final this year and challenge Federer, hasn’t played his best so far, and he’s received a lot of treatment on his back along the way.

No matter who plays Ferrer, expect a long match — and wish the winner luck the next day against Federer who, as always, looks as if he hasn’t done anything more strenuous than take a morning jog these past two weeks. Never has a man worked so hard — and concentrated so intently, as he did against a superb Roddick on Wednesday — and at the same time seemed so relaxed, so comfortable that he convinced most onlookers that he wasn’t working at all. The man who eats Big Macs might have beaten Nadal, but he’ll need a lot of luck, and a better serve, to have anything to celebrate after the final.

Mr. Perrotta is a senior editor at Tennis magazine. He can be reached at tperrotta@nysun.com.