World no 1 Rafael Nadal picked out “invincible” Novak Djokovic as his toughest opponent but also hailed the genius of old friend and on-court rival Roger Federer for his unmatched track record.

The 16-time Grand Slam winner has been a part of many an epic encounter with the Serb over the years, and the duo’s rivalry has been recognised as one of the finest in the game’s history. “What with titles and what he’s [Federer] accomplished that says he’s the best in the history of our sport. “Is he the best I’ve played against?” Well, maybe, yes.

“I’ve also played the great Djokovic, we’ve run into other really good players,” Nadal was quoted as saying at the AS awards gala.

Djokovic and Nadal have clashed in seven Grand Slam finals. The former’s win against the Spaniard in the marathon 2012 Australian Open final is widely regarded as one of the greatest matches of all-time. It is Djokovic who has a slender lead in the duo’s head-to-head record, winning 26 out of the duo’s 50 meetings.

Nadal, though, lauded the Swiss ace’s career, which comprises of 19 Grand Slam wins, “But it’d be unfair to say that Federer isn’t the best I’ve ever played against because the titles and his track record prove that to be the case. But at a technical level, when Djokovic has been at the top of his game, I have to say that I’ve been up against an invincible player.”

Djokovic, a 12-time Grand Slam winner, is on lengthy break from the game since he withdrew mid-match Wimbledon due to elbow injury. He will be back next season with a new-look coaching team.