“Roger Federer certainly is my claim to be the best of all time if there is such a thing,” said the 73-year-old Australian.
“Roger’s got all the shots, his anticipation is unbelievable, his timing off the groundstrokes with his shots, his single-handed backhand is one of the best there is.
“But at the same time, I look at Rafael Nadal and what he’s done to win seven French Open titles and Wimbledon.
“Being able to play with somewhat of a suspect knee, his way of motoring around the court and tracking shots down is quite uncanny.
“They’re very close. Are they great champions and do they have equal abilities? I’d say ‘yes’, they’re pretty much equal,” said the four-time Wimbledon champion, who was the last man to complete a calendar Grand Slam in 1969.