Sampras fears for Nadal

Nadal, 30, confirmed on Thursday that he will miss Wimbledon starting later in June with a wrist injury, having also pulled out of the French Open in the third round last month.

The veteran Spaniard, who burst onto the ATP World Tour as a 15-year-old, has been derailed by injury and form over the past few years as Novak Djokovic continues to dominate men's tennis.

And Sampras fears Nadal's hard-running style over the years is taking its toll.

"Rafa is a little more concerning to me because he's had so many miles on his legs and he's battled for so many years that each match is just a war," Sampras told Omnisport.

"And I see him just wearing down a little bit physically and mentally because he's been out there for so long.

"I feel Roger [Federer] can bounce back quicker."

Nadal boasts a 29-8 win-loss record this year, having won back-to-back titles in Monte Carlo and Barcelona, while he finished runner-up to Djokovic in Doha.