Roger Federer enjoys his "shoot-out" rivalry against Novak Djokovic, and the Swiss great is facing his biggest chance yet to win his 18th grand slam.

The duo are preparing for the 42nd meeting of a rivalry that has been even, with Federer leading the head-to-head 21-20 ahead of the US Open final on Sunday.

But Djokovic leads 7-6 in majors, including winning six of the past eight when the pair have met at grand slams.

As the Serbian world number one reflected on an incredible year that has included reaching all four major finals, Federer's chances are running out.

The 17-time grand slam champion has reached five grand slam finals since 2011, good numbers but paltry in comparison to his earlier success.

Federer has enjoyed several rivalries throughout his illustrious career, but his one against Djokovic is unlike any other.

In perhaps a greater insight into the way Rafael Nadal changed his game, Federer said having the Spaniard during his career had helped him develop and change.

Nadal's spin, particularly off the forehand side directed at Federer's one-handed backhand, had led to adjustments from the Swiss great.

"I see more of a generation of, you know, [Lleyton] Hewitt, [David] Nalbandian, [Andre] Agassi, [Tim] Henman, guys I had trouble with at the beginning. I felt they made me better a player," he said on Friday.

"Same with my generation coming up, [Juan Carlos] Ferrero, [Marit] Safin, [Andy] Roddick, Hewitt. I was trying to hang on with them and trying to be that next wave of players making it to the top, and everyone made it to world number one before me.

"I think that was very motivational for me. Made me a better player. I definitely think Rafa had a big effect, as well. Had to adjust and change so many things playing against him, preparing against him, thinking about it when I was practicing. He's probably been the guy who challenged me the most with that.

"Novak it's been more straightforward, my opinion. That's what I like about the rivalry. I don't know how it is for him, but I feel like he doesn't need to adjust his game as much, either. I think it's just a straight shoot-out, and I think that's the cool thing about our rivalry. It's very athletic.

"We both can handle each other's - whatever we present to one another, and I think our matches, it's very even. That's it, I think. I don't need to add more here."

With the Flushing Meadows courts playing faster than usual, suiting Federer's aggression and shot-making, the US Open seems a perfect chance for the 34-year-old.

And shoot-outs make for great entertainment. Expect Sunday to be no different.