The luckless Juan Martin del Potro looks set to miss the ATP Finals after suffering a fracture to the patella of his right knee.
Del Potro retired as a result of a fall during his third-round match against Borna Coric at the Shanghai Masters this week.
The world number four looks unlikely to play in the season-ending showpiece in London next month after undergoing medical examinations on Saturday.
Jorge Viale, the Argentine's spokesperson, revealed the 30-year-old was fitted with a splint on his right leg and will be informed by doctors of a recovery process in the coming days.
"It's a very difficult moment. I feel very sad. It's a hard blow that leaves me without strength," said Del Potro, runner-up at the US Open last month.
"It's very difficult for me to think about recovery again, I did not expect this to happen."