Nadal’s team issued an update on Saturday saying the arthroscopic procedure on his left psoas tendon went well, with the damaged areas cleaned and reinforced, while an old labrum injury was also addressed.
The Spaniard, who turned 37 on Saturday, suffered the injury at the Australian Open in January and had expected to only be out for six to eight weeks.
But repeated efforts to rehabilitate it did not work and last month Nadal announced he would miss the French Open for the first time since 2004.
This latest timescale means Nadal is almost certainly out for the rest of the season but he could potentially make his return in Australia in January.
He said last month he envisaged next year being a farewell tour after repeated injury troubles, with Nadal hoping to play at the tournaments that have meant the most to him.