Juan Martin del Potro, the 2009 US Open champion, plans to have an operation on his right knee in Miami, according to a statement from his team posted on Instagram.

The statement said the 31-year-old had surgery in June but now needs another procedure because of pain that wouldn’t let him run or jump, and made walking up the stairs difficult.

Del Potro fractured his right kneecap for the second time in less than a year while playing at a grass-court tournament last year to prepare for Wimbledon, and he hasn’t competed since.

The 22-time tour-level champion ended Roger Federer’s 40-match US Open winning streak by beating him in five sets in the final at Flushing Meadows 11 years ago.

The Argentine has dealt with a long series of injuries since then, mostly to his wrist and knee.

His career-best ranking was No.3 and he is currently 121st after his long absence from the tour.

Del Potro has successfully returned from injury before, winning ATP Comeback Player of the Year in the ATP Awards in 2011 and 2016.