World number one Rafael Nadal believes his current injury woes cannot be compared to those of Roger Federer and Novak Djokovic, following the Spaniard’s US Open semi-final retirement, the Daily Express report.

The 32-year-old pulled out of his last four tie against Juan Martin Del Potro after losing the first two sets.

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Nadal had his knee briefly taped up during the first set and was clearly struggling as the match continued in New York.

The Spaniard, who has had a long history of ongoing knee problems, was then rushed to his press conference at Flushing Meadows, with his injury top of the agenda for reporters.

The world number one was asked about his current injury in comparison to rivals Djokovic and Federer, who have had issues in the last two years.

Sorry, but is not fair to compare myself with them.

Novak had something last year. Roger had a couple of ones. But at the age of 36 is not the same.

You can go to the history and you can compare how many Grand Slams I missed in my career, Masters 1000s, you can compare how many they missed.

Sorry, but is not the real comparison.

Del Potro is now set to face Djokovic in the final in New York, with the Serb looking to make it back-to-back Grand Slams at the end of the season.