When Rafael Nadal advanced to centre court yesterday, the rivalry that everyone in tennis had hoped for, finally arrived. Nadal has been dogging Federer's steps for the last three years, but last year at Wimbledon Federer made it known that Nadal may be the King of the Clay Court Sandbox, but Roger still ruled the playground. His convincing dismantling of Rafa seemed to indicate that Federer was still peerless on three of four major surfaces.

Not so this morning.

Nadal's stunning early play in the first and second sets demonstrated that play on grass was no longer a mystery to the Mallorcan. How much playing six straight days on grass benefited or hurt his game we may never know, but the way he rushed the net and deftly delivered half-volleys took everyone, including Federer, by surprise. The Swiss maestro was clearly undone in the fourth set, as much by his surprise at Nadal's play, as by Hawkeye, the electronic line review system.

Easily one of the best matches of the last seven years, it signals the arrival of a rivalry that has been long if the offing. No longer is Roger Federer the default favourite, nor is the No.1 ranking without doubt. There is a very real possibility that Nadal could take the U.S. Open, as there was the moment when it looked like Wimbledon was in his grasp - you could see it plainly on Federer's face.

This fall, Flushing Meadows will be a very interesting place.