Rafael Nadal reveals what caused latest knee injury with Roger Federer clash in doubt express.co.uk

It's not about only during the tennis careers that I am worried," he added. "When I see some old legends walking around the tour, it's tough." Nadal insists he will do his best to recover in time to face Federer, saying: "I will try my best to recover – these are the matches I want to play. "To play against my biggest rival at the later stages of our careers and to keep competing against each other is great." The Federer-Nadal rivalry is one of the greatest in tennis history, with the pair set for the 39th meeting of their careers. Nadal edges the head-to-head having won 23 of the 38 encounters, with Federer triumphing on only 15 occasions.