Cape Town - Swiss tennis great Roger Federer will struggle to add to his record tally of 20 Grand Slams, the uncle and former coach of long-time rival Rafael Nadal has said.
Via a column for El Pais, Toni Nadal feels the new generation of players have made a "quality leap".
"I find it hard to see Federer raising another Grand Slam trophy," he wrote. "I do not say it for his game, although I do say it for the toughness of the five-set tournaments."
The 37-year-old Federer won his 20th major at this year’s Australian Open, but struggled to maintain that form throughout 2018.
He was beaten by 21-year-old Alexander Zverev in the semi-finals of the year-end ATP Finals in London last week, with the young German going on to take the title by beating world No 1 Novak Djokovic in the final.
Toni Nadal did however note that Federer had proved him wrong in the past.
"I have to confess that I said that on other occasions and the Swiss, repeatedly, surprised me."
Federer did not win a Grand Slam for four and a half years before he won the 2017 Australian Open by beating Rafael Nadal in the final.
Federer also won the 2017 Wimbledon title, before defending his Australian Open crown earlier this year.
But Toni Nadal added: “For some time I had my doubts about whether the youngsters would be able to overcome the game of Federer on grass, the one of Djokovic on fast courts and the one of Rafael on clay.
"And I had the impression that the change would be caused rather by the decline of some than by the attack of others. The final in London has made me think about it.
"For now, for the coming year, I trust in the full physical recovery of Rafael. I feel new episodes of his rivalry with Djokovic and, in general, a more open panorama with the definitive incorporation of the new generation."
Rafael Nadal is behind Federer on the Grand Slam tally list with 17, followed by Djokovic and America’s Pete Sampras on 14.