"Without doubt he's the best player this year, no question," Djokovic said.

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 that 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 - Djokovic 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 the Serb, Nadal admitted he would have been happier to see someone else on the other side of the net tonight. "I prefer to play against another one, but it is what it is," he said.

"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 kinds of matches, you feel special. Even if I lost that final in Australia, I feel happy to be involved in that match."

Djokovic is playing in a fourth successive US Open final, fifth in total and 12th major championship of his career.

He made the final by edging Stanislas Wawrinka in a five-set semi-final in what was his 14th consecutive run to the last four at a grand slam.

It is also his 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.

Djokovic is already guaranteed to retain the world No 1 spot whatever happens tonight.

He will enter the final having to quell his irritation at having to play on a Monday when he has a Davis Cup semi-final to play against Canada starting on Friday.

"I don't see why the US Open should get an exception. Monday finals don't go in the favour of the players who are playing Davis Cup, and I have been playing Davis Cup semi-finals for the last few years," he protested.

But he will push his concerns aside to meet the unique challenge of facing Nadal, 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 the Serb.

"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."

Nadal also has an extra incentive to win tonight - 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 Nadal, 27.

"We feel that we deserve it. I was disappointed, because we felt that we were in a good position," he said.