World number one Rafael Nadal pulled out of the Paris Masters on Friday due to a knee injury and put doubt over his status for the ATP World Tour Finals.
The 31-year-old was due to face Filip Krajinovic in the round of 16 on Friday, but said he was suffering from a right knee problem and pulled out before the match.
“I am sad to pull out from here,” the Spaniard said.
Nadal said he going for treatment in order to return for the end of season ATP Tour Finals, which take place in London from 12-19 November.
“I’m going to do my treatment, do my best to be playing in London, but I cannot talk about that now because (it) is a day that is tough enough for me to pull out from here,” said the 16-time Grand Slam champion.
World number 77 Krajinovic, who had never been past the second round of a Masters tournament before, now progresses to his first ATP semifinal of the season against either Juan Martin del Potro or John Isner on Saturday.