Roger Federer will not be losing any sleep over whether Rafael Nadal can match his record 20 Grand Slam singles titles, according to his long-term coach Severin Luthi.

The Spaniard claimed a 12th French Open title this year followed by the US Open this month to close in on the 38-year-old Swiss.

His recent success has re-energised the GOAT (greatest of all time) debate with Nadal, who has 19 slams, looking back to his very best.

Never in his career has Nadal been only one Grand Slam title behind Federer, who squandered two match points against Novak Djokovic in this year’s Wimbledon final.

“No, I don’t think he stresses (about Nadal catching him up),” Swiss Luthi, who has toured with Federer since 2007.

“He focuses on himself. He has a lot of respect for Rafa and knows what it takes to win that many titles.

“I don’t see him in any way stressed. He won’t be completely destroyed if Rafa makes the 20.”

Nadal (L) lost in four-sets to Federer in this year's Wimbledon semi-final Nadal (L) lost in four-sets to Federer in this year's Wimbledon semi-final Nadal (L) lost in four-sets to Federer in this year’s Wimbledon semi-final

Luthi said tennis fans should savour watching the two greats, rather than obsess about who is superior.