Tennis great Pete Sampras has concerns about fellow 14-time grand-slam champion Rafael Nadal, whom he fears may be suffering from burnout.
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.