The US Open, which began here yesterday, is arguably the most demanding of all the Grand Slam tournaments. The heat and humidity can be intense and the scheduling cruel. It is the only major where the men's semi-finals and final are played on successive days on the final weekend.
Peak fitness is essential, which is why Tim Henman is expecting big things of his fellow Briton, Andy Murray, who was preparing yesterday for his opening match against Latvia's Ernests Gulbis.
Having spent two weeks training under the fierce Miami sun before playing nine matches in 12 days at the recent back-to-back Masters Series tournaments in Montreal and Cincinnati, the 22-year-old Scot should be well equipped to handle whatever New York throws at him.
"I would back him against most guys when it gets into the fifth set," Henman said. "The men's game is such now that if you're not a great athlete and in great shape you're not going to be able to compete. I'm not saying that the other guys out there aren't good athletes, but I think the combination of the work Andy has done physically and the confidence that he's got from his wins mean he has no qualms about playing for three or four hours – or for however long it takes.
"I found it laughable three or four years ago when people said that he had a fitness problem. It was rubbish. He was 17 and was playing a level of tennis that was way ahead of his body. He needed to develop physically before he could do that work. I said at the time that there was no way he was ever going to have a physical problem.
"Now, with the work that he's done the effect it has on his game is clear. You can see it in his serve. The fact that he's so much stronger in his legs, which is where 60 or 70 per cent of your power comes from, helps him a lot.
"In the past he would serve well for a set or so and then maybe get a little bit tired and he wouldn't get as much drive into his serve and his percentage would dip. Now he's serving so much better. He is always going to be breaking serve a lot because his baseline game and his return are so good. If you're holding serve all the time that's such a good combination."
Murray arrived at Flushing Meadows last year as the world No 6, with six titles to his name and a quarter-final appearance at Wimbledon his best performance at a Grand Slam tournament. In the intervening 12 months he has climbed to No 2 in the world, won seven more tournaments and improved his best showing at three of the four Grand Slam events, the pinnacle being his run to the final here last year.
Is there any danger that he might have peaked too soon this summer, having won in Montreal and reached the semi-finals in Cincinnati? Henman, who was speaking as an ambassador for the HSBC Road to Wimbledon competition, said: "You have your priorities and the Grand Slams are obviously Andy's ultimate goal, but I think he wants to win every single tournament he plays in.
"I don't think it's necessarily a question of peaking. Of course he'd rather win the US Open than Cincinnati, but he'll do everything he can to win every tournament he plays. If there was a question mark about his fitness then you might wonder whether he would recover in time. But he's in as good a shape as he has ever been and probably in as good a shape as anyone out there."
Murray has beaten Gulbis in all three of their meetings, including the second round at Wimbledon this summer. The 21-year-old Latvian was talked about as a major talent a couple of years ago but has slipped from a career-high No 38 in the world rankings to his current position at No 95. He has not won two matches in a row this year.
Nevertheless he remains a threat with his big-hitting game. Murray said: "The wrong way to play him is to hit every ball as hard as you can and look like you're playing incredibly aggressively because that's what he likes. He likes a lot of pace coming at him because he hits the ball like that. It's important not to give him a rhythm, to hit some slice. He doesn't like coming to the net as much. You need to make him play a lot of balls because he gets impatient. That's really the way you go about it – it's not about smashing winners all over the court."
Murray added: "He's obviously got a big game and he's had some big results, but the consistency is something that he's struggled with a little bit. You never know when guys come through. Sometimes they have good years and then drop back."
Flushing flow: US Open record
2005 R (A Clement); 2006 4R (N Davydenko); 2007 3R (L Hyung-taik); 2008 Final (R Federer)
No 1 in waiting The verdict on Murray
"The expectations are higher now that he's No 2 in the world, but I would be surprised if he didn't do really well. He's got a tricky first couple of matches. I know he handled [Ernests] Gulbis pretty easily at Wimbledon, so you would expect him to do the same, but Gulbis is more comfortable and perhaps more dangerous on this surface. [Ivo] Karlovic is his third-round opponent and anyone who plays him finds life pretty miserable for a time. He has more to work with than Karlovic and I expect Murray to have a great run." - John McEnroe
"He's a wonderful player and he's had an incredible streak on hard courts. He's just been very consistent and it takes a great performance to beat him these days." - Roger Federer
"He's definitely a player who can win Grand Slam tournaments and if he's not going to do it this year I think he has a very good chance next year to win Grand Slam titles. He's going to be up there fighting with [Rafael] Nadal and Federer from now on and one day he might be the No 1 player in the world." - Bjorn Borg
"With all the progress he's made, particularly physically, he should win a Grand Slam title soon. He's more consistent than he was a year ago. He hits the ball harder than he used to. The biggest difference is that he's more consistent physically. He keeps going in long rallies, plays with a lot of intensity. He's hard to play against because you never know what he's going to do." - Jo-Wilfried Tsonga