Roger Federer may be just 23 years old but he is already in danger of exhausting all the challenges that his sport has to offer.
The level of his play during the US Open final against Lleyton Hewitt was remarkable, and the quality of the first set in particular can rarely have been matched.
Victory gave him his third Grand Slam title of the season - joining Mats Wilander and Jimmy Connors as only the third man to achieve the feat since the Open era began in 1968.
Melbourne, London and now New York have been conquered, with only Paris outstanding - and who would bet against a French Open title next June?
One by one, Federer is ticking off all the challenges in front of him and quashing the few doubts remaining about his pedigree.
Coming into the US Open there had been suggestions that the low-key Swiss might struggle in the bear-pit atmosphere of Flushing Meadows.
And he said afterwards: "If you can handle New York, you can handle anything."
As former champion Wilander said after watching Federer match his 1988 feat: "Physically and mentally he has the advantage over the other players.
"At the moment, I don't see anyone who can beat him."
Certainly, there is no-one out there at the moment who looks capable of beating him on the big stage; something Hewitt admitted after his defeat.
"I don't think anyone (could have beaten him)," said Hewitt. "Maybe Pete Sampras."
Sampras is the name that keeps cropping up when Federer's potential is discussed, as it is only two years since the American moved to the top of the all-time list with his 14th Grand Slam.
For Federer, there remain three serious targets: winning the French Open, overhauling Sampras and, most ambitious of all, winning a Grand Slam of all four majors in one season.
The first of those is more than realistic, at the moment it is a likelihood, although only hours after winning in New York he was not keen to discuss Paris in the Spring.
"I don't want to put pressure on myself by saying, 'Next year, your only focus is the French Open,"' said Federer.
"I have enough years left for to maybe accomplish that as well, but that's not my priority right now."
GRAND SLAM TITLES
14 - Pete Sampras
12 - Roy Emerson
11 - Bjorn Borg
10 - Rod Laver
8 - Jimmy Connors, Ivan Lendl, Andre Agassi
7 - John McEnroe, Mats Wilander, John Newcombe
6 - Boris Becker, Stefan Edberg
5 - Ken Rosewall
4 - Roger Federer, Manuel Santana, Guillermo Vilas, Stan Smith, Jim Courier
With four Slams at the age of 23, with a game capable of winning on any surface, and with a serious mental edge over all his rivals, there is every chance he will eventually beat Sampras' record of 14 Slams.
Again, Federer dampened increasingly fevered speculation.
"It's not a goal for me to beat Pete's record," he insisted. "For me that is not the motivation."
The last challenge, to match Rod Laver and Don Budge by winning all four Slams in one calendar year, is not something Federer will have to play down.
It will take more than his brilliant play, it will take plenty of good fortune to win 28 consecutive five-set matches over nine months in four different cities.
"This is a demanding sport, that's why I'm grateful for every tournament I win, or every Grand Slam," said Federer.
"You never know when it might be your last. One injury, whatever it takes, and your career can be
destroyed. I'm conscious of that."
The only man not playing the speculation game is the man himself.