Del Potro beat Federer in the 2009 US Open final
US Open champion and world number five Juan Martin del Potro faces a lengthy lay-off after undergoing wrist surgery in the United States on Tuesday.
The Argentine, 21, suffered with tendinitis in his right wrist as far back as October and has not played since January's Australian Open.
He underwent surgery in Minnesota before returning home to Tandil, Argentina, to recuperate.
"The recovery time will be long," he said after the operation.
"The surgery has left me more relaxed because although a long time will pass, I'll be able to return to the courts.
"I don't know in what ranking position I'll return, the only thing I think about is coming back and having fun."
When he won the US Open last September, the Argentine became the first man other than Rafael Nadal to beat Roger Federer in the final of a Grand Slam tournament.
Del Potro suffered a recurrence of the original injury at the Kooyong exhibition event in the new year ahead of the Australian Open and continued to struggle with the problem at the Grand Slam event, losing in the fourth round to Marin Cilic.
There have since been several dates for a possible return but on arrival at the Mayo Clinic in Rochester, Minnesota, it was decided that surgery was the best option.
Del Potro is now certain to miss the French Open and the rest of his season appears in doubt.