World No.1 Rafael Nadal has made a surprising call in regards to the toughest opponent he's ever played against.
The Spaniard admits Federer is the greatest player he's ever faced in terms of titles won, but he relegates the Swiss Maestro in another important aspect.
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Asked whether Federer was the best player he’s ever come up against, Nadal told SER: "Well, it’s complicated. 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.
"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 has a brilliant overall record against Federer, leading 23-15 head-to-head.
However it's not as good against Djokovic, with the Serb leading 26-24 against Nadal.
Djokovic has plummeted down the rankings to be currently World No.12, but will return from an elbow injury in early 2018.
At 36 and 31 respectively, Federer and Nadal overcame age and lengthy injury layoffs to split the four grand slams two apiece for the first time in a magically retro 2017 season.
Despite losing all four times to his great rival, including an epic five-set Australian Open final, Nadal edged Federer to snare the year-end No.1 ranking.
Federer settled for being the oldest year-end No.2 in history after a tour-topping seven titles, including an eighth Wimbledon crown - without dropping a set for the first time.
As the owner of one of the most astute minds in tennis, Aussie great Lleyton Hewitt was asked on Wednesday if the grand old stagers could continue dominating in 2018.
"You wouldn't think so but I don't know if those two are normal, especially Roger," Hewitt said.
"At his age, he's wound back the clock. Even against Rafa, he's done the best he ever has against him.
"I wouldn't say there's anything those two can't do."
While he's not doubting Federer and Nadal, Hewitt says question marks surround the likelihood of their fellow big-four rivals Novak Djokovic and Andy Murray return from their own injury-enforced breaks.
Neither six-times Australian Open champion Djokovic or five-times Melbourne Park runner-up Murray have played since Wimbledon in July.
Djokovic has slipped to 12th in the world after battling a long-standing elbow injury, while Murray is 16th as he struggles to overcome a chronic hip complaint.
"I don't know if they'll be as dominant as they were," Hewitt said.
"For them to pick up where they left off a couple of years ago is not that easy.
"But I would never right those guys off. They've played so well in Australia in hot conditions and also in night matches on Rod Laver Arena.
"If they can get through that first week and give themselves a chance, then they'll be tough to beat."