Argentina star Juan Martin del Potro is a doubt for next month’s Nitto ATP Finals in London.

The 30-year-old suffered a fractured kneecap during the Shanghai Masters and he will now be undergoing treatment to try and resolve the issue.

Del Potro retired from his third-round match on Thursday against Borna Coric and recent scans have now shown he sustained a fracture of his right patella bone.

The news will come as a blow to both Del Potro and the fans due to his recent form. After years of injury problems he had looked back to his best after reaching the world’s top four.

He reached the final of the US Open and China Open earlier this year but the Tandil-born star may miss a sustained period of the season.

The ATP have confirmed doctors will assess him in the coming days and Del Potro admits he is gutted with his latest setback.

He told atpworldtour.com: “It’s a very difficult moment. I feel very sad. It’s a hard blow that leaves me without strength.

It’s very difficult for me to think about recovery again, I did not expect this to happen.

“During the match I had a bad fall. I made a weird movement with the knee and hit the floor very hard. I felt intense pain.”

Next month’s season-ending ATP Finals take place from November 11-18, while the first major, the Australian Open, begins on January 14.

Novak Djokovic is the 2.50 favourite after winning the Shanghai Masters.