Federer, 36, is nearing the latter end of his career but boasts a brilliant 20 Grand Slam titles.
The Swiss star became the oldest man to ever reach the top of the world rankings as he won the Rotterdam Open last month.
However, arch-rival Nadal, 31, has 16 Major tournament wins to his name and is only one season away from closing the gap.
And with age not on his side, Federer feels that the Spaniard will one day catch his tally if he gets on a good run.
“No, not at all,” he told the Washington Post when asked if his lead over Nadal was safe.
“I just feel like today we’re all so good on clay, grass, and hard courts, if you get on a roll you can rack up some titles.
“It’s not as safe as it was in, say, the 1980s.”
Flash back 12 months and Federer was just returning from a long-term injury which saw him drop down the world rankings.
Some pundits and supporters questioned if he would call time on his illustrious career.
However, Federer admitted that he has never had that conversation with his coaches.
“It was never — ‘What do you guys think? Is this over?’,” Federer added.
“I never had that. I felt I was too close to winning.
“I was too close to the top.
“I was too close to still beating the best.”