Novak Djokovic playing carefree ball

NEW YORK -- If Novak Djokovic is feeling the pressure of playing the favorite here at the U.S. Open, he's not showing it.

Thursday afternoon, after a light hitting session before his quarterfinal match against Juan Martin del Potro, he was kibitzing with the security guard outside the locker room.

"Yeah, what's up, boss?" said a smiling, jocular Djokovic. "Hey, boss, what's up? It's all good. It's all good. It's all good."

Six hours later, it was better than good.

In a fierce, sometimes brilliant battle of former U.S. Open champions, No. 2-seeded Djokovic defeated No. 7 del Potro 6-2, 7-6 (3), 6-4. In this three-hour-plus match, Djokovic repeatedly muted del Potro's power with breathtaking defense.

The second set alone required 84 minutes (the second-longest of the year), prompting four-time U.S. Open champion John McEnroe to say from the ESPN2 broadcast booth it was one of the best sets he had ever seen.

Djokovic was still breathing heavily a few minutes after the match.

"Even though it was a straight-sets win," he said, "it was much closer than the score indicated. I was lucky in the second set. I'm really happy to be in the semifinals."

Thus, the draw has delivered on its promise: In Saturday's semifinal, the 25-year-old Serb meets the dogged No. 4 seed David Ferrer, who earlier beat Janko Tipsarevic in a fifth-set tiebreaker. That scintillating match went 4 hours, 31 minutes.

There was a sense of order in the procession to the quarterfinals. Seven of top eight seeds got through, the first time in the Open era it happened at the U.S. Open.

But then No. 1 Roger Federer was taken down by a possessed Tomas Berdych on Wednesday night. It was the first time in nine years that Federer hasn't reached at least the semifinals here. Coupled with the absence of Rafael Nadal and his aching knees -- he played in the final the past two years -- this one feels a little strange.

With Berdych meeting No. 3 Andy Murray in the other semifinal, Djokovic represents the old-school establishment. This was the 10th consecutive Grand Slam semifinal for Djokovic, tying Rod Laver and Ivan Lendl for second on a list that goes back to 1925.

Coming in, del Potro found himself burdened by a daunting disadvantage. He had spent nearly twice as much time on court as Djokovic: 11 hours, 43 minutes compared to only 6 hours, 2 minutes. They split their last two matches, with del Potro winning the Olympic bronze medal match, but Djokovic beating him last month in Cincinnati.

Del Potro came out firing three aces in his first service game, but Djokovic is regarded by some as the best returner the game has ever seen. It took him only one game to solve the riddle. After two unforced errors, del Potro hit a 131-mph bomb, which Djokovic barely got a racket on. But then del Potro shanked an easy forehand into an open court for another error. A forehand winner on a high-hopping ball gave Djokovic the margin he would need to win the first set.

Late in the set, there was a telling moment when del Potro was visited by a flying insect on the baseline. Instead of squashing it or flicking it out of the way, del Potro scraped his racket along the court and the bug eventually climbed on. Del Potro walked to the wall behind the court, then tenderly blew it off and watched it fly away.

There is a giraffe-like quality to the 6-foot-6 gentle giant. An observer might have been moved to wonder: Does he have the killer instinct to win another major? To put it another way, what would Djokovic have done with that bug?

It has been three years since del Potro won the title here. He's the only man not named Federer, Nadal or Djokovic to win one of the past 30 majors. But, set back by a serious wrist injury, he hasn't been to a major semifinal since. Based on his play in the second set alone, however, he'll return to that level next year.

Del Potro broke Djokovic in the very first game, but soon gave it back. Serving to force a tiebreaker, del Potro played as good as he can play. It took more than 17 minutes, but he did it.

"I kept on being positive," Djokovic said. "I had [three] set points and he came up with some big serves and forehands. I'm just happy to get through."

The tiebreaker was terrific, too. It was 3-all when Djokovic stopped playing and challenged a ball that was called good. He was right; it was out, and he led 4-3.

A big serve gave him a 5-3 lead and then the point of the tournament unfurled, a wild, scrambling affair that ended when del Potro's desperate lob sailed long. He hung on the net, head down, heaving, and he must have known it was over. On the next point, it was, when Djokovic's defense turned on a dime into a backhand winner.

The expected break in the third set came quickly, in the first game, and Djokovic was headed home.

Don't look now, but Djokovic has won the past three Grand Slams played on hard courts. The fourth looks entirely doable. What does Djokovic expect?

"Another big battle, obviously," he said. "It's a semifinal and David Ferrer is one of the most consistent players in the past five, six years. People don't talk about him too much, but I expect a great match from him."

Expect one from Djokovic, too.