Toni Nadal has labelled Roger Federer the 'best of all time' owing to his achievements on the professional tour and in the Davis Cup.

The Swiss ace is widely considered the greatest of all time and that claim was further strengthened after he picked up his 20th men's singles Grand Slam title in January this year and then return to the top of the ATP singles rankings earlier this month.

Australian tennis legend Rod Laver is another player mentioned in the same breath, owing to him having completed the calendar Grand Slam on two occasions. Rafael Nadal's former coach and uncle, however, believes Federer's overall achievements make him the best ever.

Nadal, a 16-time men's singles Grand Slam champion, Olympic gold medallist and four-time Davis Cup winner, is also considered to be among the best to have played the game. However, uncle Toni, as Nadal senior is fondly known believes his nephew is second best compared to Federer, who at 36, continues to dominate the game and play at the highest level.

The Swiss maestro officially became the oldest world number one in ATP history on 19 February and Nadal's former coach has backed him to play at the top for some more time, but was uncertain when asked if the Spaniard could do the same.

Nadal's former coach believes his nephew's ability to emulate Federer will depend on his fitness, which has yet again deserted him. The 31-year-old is currently sidelined with a hip injury, which has plagued him since he pulled out in the quarter-finals of the Australian Open.

"At the moment, Roger is the best of all time. No one has done what he achieved. Rod Laver was also very good, but no one had won 20 Grand Slam titles, a Davis Cup [title] and [the rest]," Toni Nadal said, as quoted on Tennis World USA.

"Rafael [has] won 16 Majors, triumphed four times in Davis Cup, but Federer is better, he is the best! I think he can play at this level for a little more time.

"I can't say about that [yet]," he added. "But if his body is [healthy], I don't [see why not]. But, if Rafael sees the opportunity to win big tournaments, it's possible that he will play for a few more years."

Roger Federer and Rafael Nadal
Roger Federer and Rafael Nadal have a combined 36 Grand Slam titles between them Getty