By Tom Perrotta

Stan Honda/AFP/Getty Images A step-by-step look at Federer's miraculous shot.

What it must be like to be Roger Federer these days. There are no more records to break, no more burdens to carry. He's happy at home, happy on the court, and comically good when he needs to be. In a close and entertaining semifinal against Novak Djokovic on Sunday, Federer never seemed flustered and took advantage of what few opportunities Djokovic gave him for a 7-6 (3), 7-5, 7-5 victory. He'll play in his fourth major final of 2009 on Sunday, and try for his record sixth consecutive U.S. Open. His opponent, Juan Martin del Potro, who pummeled Rafael Nadal earlier in the afternoon, will contend for his first major title.

Djokovic played his best tennis of the tournament on Saturday and pushed Federer in all three sets, but Federer was more precise, more creative, and more daring in the match's decisive moments. When Djokovic served to stay in the match at 5-6, 0-30, Federer hit what he later described as the greatest shot he has ever hit in his life, between the legs and into the far corner for a winner. Federer celebrated and Djokovic wiped his nose and smirked. It was only match point, but this semifinal was over.

"Whenever he needed to serve well, he did," Djokovic said. "Whenever he needed to defend well from the forehand side or the backhand side, that's what he did."

That is, of course, what Federer does, especially at the U.S. Open, where he hasn't lost a match since 2003 (he's 40-0). Djokovic said Federer might be playing better than ever.

"He's maybe playing the tennis of his life," Djokovic said. "The way he stands on the court, the way he approaches the matches, it's different, you know. It's like more relaxed."

Del Potro could be the toughest opponent Federer has faced in a U.S. Open final. The 6-foot-6 Argentine made quick work of Nadal on Saturday afternoon. He served for the corners, rarely missed a ground stroke, and didn't drop serve once. Del Potro's 6-2, 6-2, 6-2 victory was the most lopsided defeat of Nadal's Grand Slam career.

One could hardly call del Potro elegant, but there is a smoothness to his strokes now that he didn't have two years ago. There's also a confidence about him that he lacked as recently as the Australian Open, where he lost two love sets to Federer in the quarterfinals. Since then, though, del Potro has improved on the form that earned him a 23-match winning streak, including four straight titles, last season. He's a bruising player, a man with devastating power on both his forehand and backhand and a serve that consistently breaks the 130-mph barrier. He's also well rested, unlike last year, when he struggled physically in a quarterfinal loss to Andy Murray.

Del Potro has not beaten Federer in six meetings, but their last match, in the French Open semifinals, was their closest (Federer won in five sets). Perhaps being Argentine will help. The last man to defeat Federer in Flushing, of course, was David Nalbandian.

Tom Perrotta is a senior editor at TENNIS magazine. Follow him on Twitter.