New York - World number one Novak Djokovic believes he is about to face the "ultimate challenge" in tennis when he tackles Rafael Nadal for the 37th time in Monday's US Open final.
The top-seeded Serb is playing in a fourth successive final in New York, fifth in total, and the 12th major championship of his career.
Despite being angry at having to play the final on a Monday, he will be buoyed by having won the pair's last three Grand Slam finals played on faster courts - Wimbledon and the US Open in 2011 and the 2012 Australian Open final.
"Facing Nadal is the biggest challenge that you can have in our sport. He's the ultimate competitor. He's fighting for every ball and he's playing probably his best tennis ever on hard courts," said Djokovic.
"He has got injuries, many injuries, on this surface, but now he looks fit. But I have played him already here twice in the finals. I know what I need to do."
Monday's match will be Djokovic's third major final of the season after seeing off Andy Murray, who was the defending champion in New York, in Australia before being overwhelmed by the Briton at Wimbledon.
He is already guaranteed to retain the world number one spot whatever happens on Monday.
Meanwhile, Nadal will attempt to crown the year's most compelling comeback with a victory that once would have seemed unlikely.
Twelve months ago, the swashbuckling Spaniard, who will be playing in his 18th Grand Slam final, sat at home in Manacor, nursing his troublesome knees and fearing his career may be finished at just 26.
But after seven months out of the sport, Nadal has been a revelation.
He has won nine titles, including a record eighth French Open to take his Grand Slam haul to 12, stacked up a 59-3 victory run as well as a perfect stretch of 21 wins on hard courts.
"With no doubt he's the best player this year, no question," admitted Djokovic.
Nadal leads Australian Open champion Djokovic 21-15 in a career rivalry that began at Roland Garros in 2006.
Their 37th meeting will be a record on head-to-head meetings, beating the 36 duels that John McEnroe and Ivan Lendl fought in their careers.
Nadal has won five of the last six meetings, a stretch which started after Djokovic won their epic 2012 Australian Open final, played out over a gruelling five hours and 53 minutes.
One of Nadal's wins was in a pulsating French Open semi-final in June where Djokovic led 4-2 in the final set before Nadal hit back to keep the Serb still waiting for a maiden title in Paris.
Both men will be chasing their second title in New York - Djokokic was champion in 2011, beating the Spaniard the year after Nadal completed his career Grand Slam in the city by seeing off the Serb.
Despite his mastery over Djokovic, Nadal admitted he would have been happier to see someone else on the other side of the net on Monday.
"I prefer to play against another one, but it is what it is," said Nadal.
"I want to play against a player where I have more chances to win. But 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. Even if I lost that final in Australia, I feel happy to be involved in that match."
Nadal also has an extra incentive to win on Monday - to rescue bruised Spanish pride at Madrid's failure to win the right to host the 2020 Olympics.
"It's very hard and tiring for all of us, because the country and the city of Madrid worked a lot to have the chance so many times," said the 27-year-old.
"We feel that we deserve it. I was disappointed because we felt that we were in a good position."