If there is a time, it is now. Federer and Nadal have played each other 21 times. Eight of those matches have been at Grand Slams, seven of them in finals. But in seven years of joint appearances, they have never met at the U.S. Open.
The fault has not been Federer's. The Swiss has made the final for six straight years, winning 2004-08. He is expected to have few problems kicking off this year's campaign against Argentine Brian Dabul in the first round and, on recent form, should not be threatened until at least the quarterfinals.
But Nadal has never advanced far enough to meet Federer at Flushing Meadows, his best effort being two semifinals in 2008 and 2009. A win would give him a career Slam, making the Spaniard just the seventh man to win all four majors at least once.
"I'd love to play him," Federer said. "We've played in all the other majors, so this one's missing. I hope we can do it this year, otherwise I think we'll both be around for quite a bit longer that we'll have a chance further down the stretch."
Nadal shared Federer's sentiments.
"I would like to play against him in this year because I can only play against him in the final," Nadal said.
"[If] we play in five years, maybe we can play in third round."
"In five years." Clearly Nadal sees no imminent decline for the two, either. But it is a reminder that their names will not always sandwich the draw as they do this year, and only a few chances might be left for a title bout in the only major they have never contested.
Only the No. 1 and No. 2 seeds in a tournament are guaranteed not to meet before the final, and Federer and Nadal have each dropped to No. 3 at various times this season. At the top of the game, even a short stutter can be costly. Nadal was laid low with midseason injuries last year, and Federer dipped in form after winning the Australian Open earlier this year and had quarterfinal exits at the French Open and Wimbledon. Their meetings also have become less frequent -- just one in the past 14 months, at the Madrid Masters in May.
But for the moment, the now-legendary rivals have re-established their stranglehold on the men's game. After Federer won in Australia, Nadal took over when the clay season began, going undefeated on his beloved red dirt in Paris and following up with a win on the slicker grass courts at Wimbledon.
Federer re-emerged as the tour returned to hard courts a few weeks ago, reaching the final of the Toronto Masters and winning the Cincinnati Masters. He, too, relishes the prospect of a meeting with Nadal in two weeks' time, on the faster hard court that he believes favors his game over the Spaniard's.
So why hasn't Nadal managed to set up a meeting? "There's not much he's doing wrong. If you can make it to the semis, you can make it to the finals," Federer said. "I just feel maybe on average the U.S. Open could be the fastest Grand Slam. That could be one of the problems for Rafa here in the past."
Although Nadal feels there is "no question" that Wimbledon's grass is still faster than the hard courts at the U.S. Open, he has had more problems adapting his clay-court-optimized game to it. "The ball is softer. The ball doesn't get that topspin that I like to play with," he said. "The center court is difficult to play more wind than the rest of the Grand Slams."
Nadal has yet to show his best tennis in the summer hard-court swing, losing in the semifinals of Toronto and the quarterfinals of Cincinnati, and his draw at the U.S. Open suggests he will face a succession of dangerous shot-makers on his way to a possible semifinal against Andy Murray.
But the Spaniard also has had his share of success on the U.S. Open's DecoTurf surface, especially in 2008, when he won on it at Toronto and the Beijing Olympics but was "destroyed mentally" by the time he reached the U.S. Open semifinals. With no Olympics on the schedule this year, Nadal should have more in reserve.
After losing to Juan Martin del Potro in five sets last year, Federer is determined to return to the final and win it this time around -- no matter who is across the net. "Maybe there is an extra incentive for me to win it again after being two points away last year," said Federer, who will be going for his 17th Grand Slam title. "It was a disappointing loss for me. I felt like that was one of the finals I should never have lost. At the end, del Potro played great and deserved the victory. It was a tough one to swallow."
Don't mark the Swiss and the Spaniard down for a meeting two weeks from Sunday just yet, however. Murray defeated Nadal and Federer on his way to winning in Toronto and joins them as part of a three-man group of favorites. Although officially coachless at the moment, the Scot has part-time coach Alex Corretja as well as his canny tennis coach mom, Judy, with him for the tournament.
Other men lurk further in the background, such as this year's draw-busters Robin Soderling and Tomas Berdych and increasingly mysterious Novak Djokovic. The home hopes are carried by Andy Roddick, red-hot Mardy Fish and Sam Querrey, whereas John Isner's participation and prospects are dimmed by an ankle injury.
Federer and Nadal have won the three majors played so far this year, as they have all but two majors since the French Open in 2005. Nadal is healthy; Federer is in form. The chances of their long-awaited meeting in the Big Apple have never been better.
Kamakshi Tandon is a freelance tennis writer for ESPN.com.