MELBOURNE, Australia -- History.
For all the money now available in top-level tennis, the top players are motivated by titles. And the very best players of all time are driven by the thought of Grand Slam titles. Because winning Grand Slams means history.
Sometimes, the stars align so that history-makers are all in the same place. When the Australian Open begins Monday, Roger Federer, Rafael Nadal, Novak Djokovic and Serena Williams will all be striving for yet more historic achievements.
As four of the greatest players to ever play tennis -- perhaps the four best -- almost everything they do is linked to their place in the history books, every win adding to their legacy, their place in the pecking order.
But this year's event is even more special, simply because of the numbers.
Should Williams win her eighth Australian Open, the American will equal the record of 24 Grand Slam titles held by Australian Margaret Court, who will be ever-present this year, 50 years after she won all four majors for the Grand Slam.
When Djokovic won the title here 12 months ago for his 15th Grand Slam, he immediately set his sights on chasing down Federer at the top of the list. His win at Wimbledon took him to 16, three behind Nadal, whose Roland Garros and US Open have him at 19, one behind Federer at 20.
It's a delightful thought, and not an impossible one, that Federer, Nadal and Djokovic could all end up with the same number of Grand Slam titles, which might be fitting given that each has been pushed to greater heights by the others.
"I think that kind of rivalry, that has been special, has brought us to these tennis heights we have at the moment," Djokovic said on the eve of the event. I think we still look at each other's games, each other's careers, and we still kind of compare our own careers to the others."
When Federer passed Pete Sampras with his 15th Slam title in 2009, Nadal had only six and Djokovic had only one. It seemed impossible at the time that anyone would get close to Federer, and yet, 11 years later, it's a bottleneck at the top and the Swiss, who is 38, seems to have accepted that he will eventually be overhauled.
"I think the way it's going, obviously, Rafa and Novak will win more," Federer told the AP. "And the season they had [in 2019], again shows that there is more to come for them.
"Now, at the end, if somebody else would pass you, I mean, I guess it's OK, because that's what sports is all about. It's a lot about numbers. It's a lot about records. But I had my moment, and I always said everything that comes after 15 was, anyway, a bonus. And especially after the knee injury [in 2016], everything that came after that was a bonus. I would have taken one more Slam, and I was able to get three more -- and three amazing ones."
Federer says he assumes Nadal and Djokovic will have some "incredible" years ahead, but Federer remains a threat in Melbourne, where he won most recently in 2017 and 2018.
Drawn in the same half as Djokovic, and with the likes of Canadian Denis Shapovalov and Matteo Berrettini of Italy in his section, it will be far from easy. Federer knows he needs to hit the ground running, having played nothing other than exhibitions since the ATP Finals in November.
"I've got to really make sure I get out of the gates quick," Federer said. "Practice has been going well. Had plenty of time to pace myself and do all the things I had to do to get ready. I hope it's enough. I know it's a super long road to victory. That's why I've got to take it one match at a time. My expectations are quite low."
It was at Roland Garros last spring, where he was busy collecting the title for the 12th time, that Nadal explained his philosophy about the race to be the best of all time in terms of Grand Slam titles.
"I would love to be the one who has the most," he began. "[But] you can't be frustrated all the time because the neighbor has a bigger house than you or a bigger TV or better garden. That's not the way that I see the life, you know."
It's an attitude that has served Nadal well throughout his career, a career far longer than most people expected he would be capable of, given his physically exhausting game style.
"It's something that difficult to imagine for me because for my style of game, as a lot of people said, my career should be little bit shorter," he said. "But here we are. Happy for that. Even for me is a big surprise to be where I am at my age. So, happy for everything. Just enjoying the situation."
At the ATP Finals in London last November, Federer said he felt the new brood of youngsters on tour -- from Stefanos Tsitsipas and Sascha Zverev to Shapovalov and Felix Auger-Aliassime -- were the "real deal." And yet, considering that Federer, Nadal and Djokovic have won 55 of the past 66 Grand Slams between them and each of the past 12, the chances of anyone breaking through remains slim.
Williams, meanwhile, continues her chase to equal Court's record of 24. On the four occasions she has made a final since returning in 2018 following the birth of her daughter, the American has found one player too good on the day.
But even at age 38, she is the favorite with the oddsmakers to win the title. Her confidence was boosted by winning the title in Auckland last weekend, her first title since becoming a mother. She looks fit, and having won the title seven times, she is likely to take some stopping.
"It was very smart of her, I think, to play that warm-up tournament, and she looked good," former world No. 1 Chris Evert said on an ESPN conference call earlier this week.
"I think Serena, she certainly looks hungry, and I think she's got a little momentum going into the Australian Open, and it would probably be the least pressure, this Grand Slam, to win for her. I think she's got a good shot at winning it."
By the end of the Australian Open, the pecking order is likely to be shaken up a little more.