Rafael Nadal
Rafael Nadal has lost all five matches against Novak Djokovic this year. REUTERS

For Rafael Nadal, getting here was the easy part, to retain his US Open crown on Monday night the Spaniard must do something he hasn't done all year: beat Novak Djokovic.

Djokovic, the top seed and world number one, has got under Nadal's skin this year, beating him five times in five finals across hardcourt, clay and grass, and winning 11 out of the 14 sets during that run.

The last time the pair met was at Wimbledon, where Djokovic beat Nadal in four sets to notch his second Grand Slam title of the season following his victory his Australian Open in January.

For Nadal, Monday's final represents an opportunity to avenge his Wimbledon loss but also to reclaim the mental edge he cited as a contributing factor in losing at SW19 for the first-time in his career.

In a candid self-assessment of his current form the world number two admitted his confidence has taken a bruising this season but believes his position as underdog could provide an advantage in this evening's match-up.

"I am not very happy about my mental performance against him [Djokovic] this year," he said. "That's true, no? Because for moments I didn't believe really 100% with the victory. That's big problem. Because when that's happening, you have your chances less, much less than if you believe."

"He's obviously the favourite for the final, and I know I have to do something better than the other matches to try to change the situation," Nadal said after his 6-4 6-2 3-6 6-2 victory over Britain's Andy Murray on Saturday.

However, Djokovic remains wary of his opponent and approaches Monday's match on the back of a mentally draining five-set victory against Roger Federer. The Serb fought back from two-sets down, saving two match points in the process to beat the Swiss for the second year running.

"I have my game, and I beat him in the past playing my game," he said. "The thing is [to] play my game very well and be enough strong mentally all the time, fight every ball, believe in the victory in every moment. That's something that for moments this year I didn't [do].

"I know that I have a game that is good enough to win against him," he added. "I proved that this year in three different surfaces, so I believe that I have a good chance. I need to go out on the court believing I can win. But, you know, we're talking about a player who has won 10 majors already in his career and he's only 25."