It is the oldest debate in sport. Who is the greatest of all time? You can never, of course, produce a definitive answer, but when it comes to assessing the tennis player of all the ages you would find it hard to argue against the combined might of Pete Sampras, Andre Agassi and Billie Jean King.
In the eyes of many, Roger Federer was the greatest player ever to wield a racket even before his triumph at Roland Garros on Sunday. Now the statistics are supporting that view. In winning the French Open for the first time, Federer drew level with Sampras' all-time record of 14 Grand Slam titles and became only the sixth man in history to win all four Grand Slam crowns.
"It ends the discussion of where he fits in the history of the game," Agassi said after handing Federer the Trophée des Mousquetaires in Paris. "What he has done is unmatched."
Sampras, who watched Sunday's final on television at his home in Los Angeles, agreed. "I'm obviously happy for Roger," he said. "Now that he has won in Paris, I think it just solidifies his place in history as the greatest player that played the game."
King, meanwhile, said that Federer's achievement in equalling Sampras' record and completing a career Grand Slam "firmly places him in a special place as the greatest player of all time". She added: "He has earned his place and he has proven he belongs. Roger is a champion for the ages."
For a man with deep respect for the sport's history and traditions, there is surely nothing Federer would love more than to eclipse Sampras' record when the tennis circus heads for the All England Club's big top in 13 days' time. The Wimbledon trophy has always been Federer's most cherished prize and he will go there as the favourite, even if Rafael Nadal, the defending champion and world No 1, recovers from his latest knee problem. Should he fail to win a sixth Wimbledon title next month, it is likely only to be delaying the inevitable. At 27 Federer is in his prime.
Memories, nevertheless, can be short. Some would argue the cases for Donald Budge, the first man to win the Grand Slam (the four majors in the same year), for Bjorn Borg, the master of Paris and Wimbledon, for John McEnroe, a supremely gifted but controversial talent, for Bill Tilden or Ellsworth Vines, great Americans of the 1920s and 1930s, or for Rene Lacoste or Henri Cochet, two of France's great musketeers.
Ultimately, however, the list of Federer's challengers boils down to Rod Laver and Sampras, largely because of their sustained brilliance over so many years. Laver won Grand Slams in 1962 and 1969 and would surely have won more than 11 majors had he not spent five years in the wilderness as a professional.
Laver was an unlikely champion. He was a sickly child and at 5ft 8in had few physical advantages other than a massive left arm with which he thumped the ball, imparting more topspin than any of his predecessors. In 1969 he was all but unbeatable, winning 17 singles titles. He competed in a golden age for tennis and was one of a group of great Australians that included Roy Emerson, Ken Rosewall, John Newcombe, Tony Roche and Fred Stolle. Laver, nevertheless, had to contend with only two different surfaces when he won his two Grand Slams – the French Open was the only major not played on grass – and with far fewer full-time opponents than modern-day players.
Laver was always a hero for Sampras. "He had a few years in there where he didn't have an opportunity to win majors," Sampras said. "But you can't compare the eras, and in this era, the competition is much more fierce than Rod's."
If there is another challenger to Federer as the greatest in history it would be Sampras himself. The American's 14 Grand Slam titles spanned a 12-year period. He won the US Open in 1990 at the age of 19 and played the last match of his career when he won the title again in 2002, beating Agassi in the final. Sampras also enjoyed an extraordinary run at Wimbledon, winning the trophy seven times over an eight-year period between 1993 and 2000. The only defeat he suffered at the All England Club in that time was in the 1996 quarter-finals to Richard Krajicek, who went on to win the tournament.
Like Laver, Sampras had outstanding fellow countrymen to contend with – most notably Agassi, Jim Courier and Michael Chang – as well as the likes of Boris Becker and Stefan Edberg. Federer, in contrast, stepped into something of a vacuum when he won his first Grand Slam title at Wimbledon in 2003. Marat Safin, Lleyton Hewitt, Andy Roddick and a fading Agassi were the best of his early rivals, while in recent years Nadal has been the only player to challenge him consistently, although Andy Murray and Novak Djokovic are emerging contenders.
Like so many Americans, Sampras never fully mastered clay. In 13 visits to Roland Garros he reached three quarter-finals and one semi-final. He was in good company. The list of Grand Slam champions who never won in Paris includes Becker, Edberg, McEnroe and Jimmy Connors.
On an aesthetic level, the vote for the greatest player would have to go to Federer. Laver and Sampras were, like the Swiss, natural attackers, men who took the game to their opponents, but Federer is also the game's supreme stylist. If his forehand is the greatest stroke in modern tennis, his majestic one-handed backhand is a delight to watch, even if opponents target it as his weaker flank.
Federer's serve is perhaps the most under-rated part of his game. Speed and power are not so much the secret as disguise and variety. Robin Soderling could testify to that: in Sunday's second set tie-break Federer hit aces on all four of his service points. He is also devastatingly quick around the court. Soderling said he had never faced anyone who played as fast.
Laver and Sampras may have had the better volleys, if only because so much of today's game is played at the back of the court. Laver excelled in all areas and was as comfortable on the baseline as at the net. Sampras, who had a huge serve, was a firm believer in getting to the net, where he consistently dominated opponents. Although the American's game lacked the elegance of Federer's, he could smother opponents with the sheer force of his game.
If there is still room for debate, Federer has time to erase all doubts. He has already gone from one to 14 Grand Slam titles in half the time it took Sampras. The American won his 14th Grand Slam title at the 52nd attempt, Federer at the 40th.
Federer spoke on Sunday about how he felt a great pressure had been lifted from his shoulders with his victory in Paris. If he plays with greater freedom in future, there is no telling what he might go on to achieve. The 2012 Olympics at Wimbledon is already a target and the Swiss has talked about playing beyond that date.
Will marriage and the imminent birth of his first child change Federer's priorities? "My private life is one part of my life," he said on Sunday. "The professional one on the court is another one." His rivals have been warned.
Three kings Head-to-head
Date of birth 12 August 1971
Grand Slam titles 14
Australian Open 1994, 1997
Wimbledon 1993-1995, 1997-2000
US Open 1990, 1993, 1995, 1996, 2002
Career titles 64
Games won/lost 762-222
Date of birth 8 August 1981
Grand Slam titles 14
Australian Open 2004, 2006, 2007
French Open 2009
US Open 2004-2008
Career titles 59
Games won/lost 650-155
Date of birth 9 August 1938
Grand Slam titles 11
Australian Open 1960, 1962, 1969
French Open 1962, 1969
Wimbledon 1961, 1962, 1968, 1969
US Open 1962, 1969
Career titles 40
Games won/lost 392-99