Nadal hints withdrawal from ATP World Tour finals

World number one Rafael Nadal has hinted that he could withdraw from the ATP World Tour Finals because of a troubled knee.

Nadal is scheduled to play his opening match on Monday night against Belgian player David Goffin at the O2 Arena, London.

The Spaniard had earlier, pulled out of the Paris Masters before his quarter-final match citing a knee injury, sparking fears over his appearance in London.

"I don't have to make a decision [yet]," he said. "I'm going to play - that's what my feeling is today," the Guardian quoted Nadal, as saying.

He added, "I can't predict what might happen in the next couple of days, but my feeling is that I'm here to play and to try my best."

If the Spaniard pulls out of the event it would be a huge blow to organisers, with the likes of Novak Djokovic and Andy Murray already missing from this year's event, giving the eight-man field a lopsided look.

Star players Novak Djokovic and Andy Murray are already missing from the tournament and the Spaniard's absence could further make the ATP World Tour dull.

Meanwhile, world number 2 Roger Federer expressed that Nadal's absence would be a big blow.

"He's the No1 player in the world, had the best season of us all and is a superstar of our game. So naturally it would be a blow. If he's here, to me that's a good sign," the Swiss said.

The 19-time Grand Slam champion will open his ATP campaign on Sunday against American tennis player Jack Sock.