Novak Djokovic may have number one by his name but he knows he will face the best player in the world in tomorrow's US Open final.
Rafael Nadal has put together one of the most impressive seasons in tennis history despite only coming back in February following seven months out with knee problems.
The Spaniard has dominated in a way he did not manage even when he won three grand slam titles in 2010.
The 27-year-old has lost only three matches, and one of those was in the final of his first tournament back.
He was also beaten by Djokovic in the final in Monte Carlo, while the only real blip was a first-round defeat by Steve Darcis at Wimbledon.
That prompted more concern about the state of his knees but all Nadal really needed was time, and when he hit the hard courts of North America he looked better than ever.
The strapping on his knee was gone and Nadal has swept all before him on a surface previously considered his worst.
Remarkably, he has won all 21 of his matches on hard courts, collecting three Masters series titles and now standing one victory away from a second US Open crown.
This will be a fourth consecutive US Open final for Djokovic, three of which have been against Nadal while he was beaten by Andy Murray 12 months ago.
They have managed one title apiece in New York, Nadal winning in 2010 to complete his career grand slam and Djokovic a year later.
Describing facing the Spaniard, Djokovic said: "It's always the biggest challenge that you can have in our sport now. He's the ultimate competitor.
"He's fighting for every ball and he's playing probably the best tennis that he ever played on hard courts.
"He has got many injuries on this surface, but now he looks fit. He had seven months off. He lost three matches this year. With no doubt he's the best player of the moment this year.
"So the way he's been playing, he's very confident, but I know how to play him. Hard court is my most successful surface. I have already played him here twice in finals. I know what I need to do."
Nadal has looked marginally the more impressive here and certainly had an easier time of it in his semi-final.
While Djokovic struggled past Stanislas Wawrinka in five sets, Nadal saw off Richard Gasquet in three, although he did have his serve broken for the first time this tournament.
By getting to the final, Djokovic has guaranteed he will stay top of the rankings whatever happens tomorrow, but Nadal is almost certain to usurp him sooner rather than later.
The Spaniard has no points to defend until after the Australian Open, while Djokovic had a very successful end to last year and won a fourth title in Melbourne.
The Serbian has vowed to hang on to top spot as long as he can, saying: "It's important to me, of course.
"I have finished the year number one the last two seasons, and I know how much consistency and hard work and energy I've put into the 10, 11 months of a season you need to deliver in order to be number one.
"Rafa is I think in a better position right now but I'm fighting for it."
Nadal and Djokovic have made a speciality out of playing long and gruelling matches against each other, none more so than a near six-hour Australian Open final last year.
Asked if he was looking forward to renewing the rivalry, Nadal said with a smile: "I prefer to play against another one. We have to be honest, no? We don't have to be stupid.
"I want to play against a player that I have more chances to win. But I play against him. I played against him a lot of times. Always we played very exciting matches.
"When you are involved in these kind of matches, you feel special. And at the end, even if I lost that final in Australia, I feel happy to be involved in that match.
"It's good if both of us are playing at a very good level so the match becomes great because we play long rallies, we bring our game to the limit.
"I hope to be ready for that. I need to keep playing very aggressive and play a very, very good match."
The pair will meet for the 37th time, more than any other two men in the Open era.
Nadal leads the head-to-head 21-15 and has won five of the last six matches, but Djokovic leads 3-2 in grand slam finals.