Current world number one Rafael Nadal has said that Novak Djokovic reached a higher level of performance than Roger Federer over the course of his career.
All three athletes have held the number one position at different times over recent years, but Nadal claimed that Djokovic was at times an "invincible," opponent.
However, he found it impossible to deny that Federer was the best ever by another method of comparison, saying of the current No.2 ranked player:
"What with titles and what he’s 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.
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"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."
Nadal and Federer won two Grand Slams each in 2017 after Djokovic, Andy Murray and other top tennis players had to sit out much of the season with injury.