Editor's note: Former world No.1 and seven-time Grand Slam champion Mats Wilander is writing exclusively for Yahoo! Sports throughout the U.S. Open. The 1988 U.S. Open champ breaks down who's hot and who's not, offering his thoughts courtesy of Lacoste.
This sounds like a strange thing to say about a man who has won the U.S. Open five times in a row, but this tournament is not best suited to Roger Federer.
The world No. 1 has triumphed with such regularity in New York thanks to his fantastic aura and reputation and the fact that there have not been the players in this era ready to step up and challenge him.
However, I feel this year Federer may be more susceptible than ever to an upset defeat at Flushing Meadows, even though No. 2 seed Andy Murray was knocked out Tuesday.
The difference is that now there are some genuinely high quality hard-court players. Novak Djokovic is one, so too is Fernando Verdasco, even though he grew up in Spain. Juan Martin del Potro loves outdoor hard courts and continues to grow in confidence so the threats are piling up.
Other guys like Robin Soderling would also consider the cement at Flushing Meadows to be their ideal surface.
Then there is Rafael Nadal, already a legend on clay but a player who has adapted his game brilliantly to this surface, as he showed in winning the Australian Open in January.
Federer is still the favorite, of course, but I expect him to have a tough time now that his tournament has properly begun.
The first few rounds were so comfortable for him that he will only now consider things officially underway, three more matches left to win a sixth title.
He has the game and all the ability to succeed again, but I expect to see him strongly tested over the next few days.
MATS WILANDER'S YAHOO! SPORTS POWER RANKINGS
1. Roger Federer – had things all his own way so far
2. Rafael Nadal – fighting hard and his game looks strong
3. Novak Djokovic – is he fit enough to get through seven matches?
4. Juan Martin del Potro – constantly growing in stature
5. Robin Soderling – very dangerous on these courts