Who can beat Novak Djokovic, already the player of the season by an almighty margin, in the US Open? If he is 100 per cent fit, I doubt there is a player out there who is capable of doing it.
But this is not to say that Djokovic is a guaranteed winner. The one thing that could undo him is weariness. I don't believe he has a serious shoulder problem, even though he defaulted against Andy Murray in the final of the Cincinnati Open, but I do worry that his incredible record this season has pushed him close to the limits of his own endurance.
That is the irony of success. Look at the two back-to-back Masters titles in Montreal and Cincinnati and most of the top guys have played five or six matches, whereas Djokovic has played 10. Hard-court tennis creates a lot of wear and tear on the body.
It is a grinding style of play, and in the American summer it always seems to be hot and humid, so it is hardly surprising that he pulled up against Murray.
You can see why Djokovic wants to keep going. "Winning breeds winning" is one of my favourite axioms. Success is the only drug athletes are allowed to enjoy, and while you're experiencing it, you just want more and more. During a hot streak like this, Djokovic must feel as though he is on a constant high.
But there is one obvious downside to reaching the final of every tournament: you play so many more matches than everyone else.
I can only salute Djokovic for the way he has has maintained his performance levels. Having wonWimbledon, which was clearly the peak of his career to date, he went straight into a Davis Cup tie against Sweden. After that, I was expecting he wouldn't really be up for the first couple of hard-court tournaments.
But once again he started where he left off, beating some tough opponents in the Masters series.
Eventually he is going to run out of gas, and he has got to be careful not to do that in the second week of the US Open, when he is supposed to be playing the quarter-finals and semi-finals.
When Roger Federer was the king of New York, winning five US Open titles in a row, he was very canny in the way he structured his season to make sure that he had something left in the tank when he arrived at Flushing Meadows. He knew his own body and he knew how to balance his schedule.
But with Djokovic, this runaway success is still new. He can never have reached the end of August with 59 matches under his belt before.
That is why he and his support staff must be careful how they approach the end of the year. Djokovic is on course to match or even beat John McEnroe's incredible year of 1984, when he won 81 matches and lost three, but to get there he will need a decent run in New York. I don't expect him to play too much in the autumn.
The first week will be crucial. He needs to keep the matches quick: a couple of straight-sets wins, maybe one four-setter, and he'll make it through to the second Monday fresh.
But there aren't many easy games on hard courts. It's not like clay or grass, where there are a few specialists and everyone else feels a little uncomfortable. Just about every player is at home playing hard-court tennis, whether they are baseliners or serve-volley artists.
So what of the rest? I would always rate Federer ahead of Rafael Nadal on hard courts. Even though Nadal is the defending champion, I don't think he is going to retain his title this year. He is not yet physically or mentally back to where he was last year. His foot injury still seems to be bothering him, and he is unsure what to do about his five-match losing streak against Djokovic, especially as all of those defeats have come in tournament finals.
As for Federer, it only takes him a couple of wins to come back to his old self, but he needs to do that in a hurry. Over the last few weeks, he has lost in the third round and then the quarter-finals, and those are not the results of a potential Grand Slam winner.
Of all the guys behind Djokovic, Murray is probably the one with the most confidence and the best conditioning. He looked awful in Montreal, as if he was taking a holiday, but then he went to Cincinnati and as soon as he had a couple of matches under his belt he got stronger and stronger. In the final, even before Djokovic retired, he was the dominant player.
This has been a good year for Murray. He has cemented his place in the top four, and in effect he defended last year's win in Montreal with the result in Cincinnati. He had an average US Open in 2010 so a good result now, a semi-final or final, could be a major rankings break through. He could end up chall eng ing Federer for the No3 spot.
Remember what I said, winning has an extraordinary effect. After Cincinnati Murray – who really enjoys the fast courts at Flushing Meadows – could just be the man in perfect position to take advantage if Djokovic falters.