Rafael Nadal expects to be fit for the ATP Finals but will see how his knee reacts to practice sessions before deciding whether he can play in London.
The 16-time grand slam champion pulled out of the Paris Masters ahead of his quarter-final against Filip Krajinovic last week because of injury, putting his participation at the O2 Arena in doubt.
World No.1 Nadal said there are no guarantees he will feature in the season-ending event, but is hopeful he can attempt to win the tournament for the first time.
"Hopefully the knee is good," he said. "I've done everything I've needed to do in order to get ready for London.
"Now it's the moment to wait and practice at the O2 over the next couple of days. Let's see if I am able to be 100 per cent to compete.
"If nothing happens, then I will play. I visited my doctors after the Paris Masters – it was a tough day for me having to pull out of Paris. Pulling out of any tournament in the world is tough, but pulling out of the city of Paris is especially tough for me.
"That's how it is. I went back home and visited the doctors to do some treatment. I expect the treatment to work and be ready for here. I know I'm confident because I'm having a great season with one event to go. I am here to try my best."
Nadal is drawn to face Dominic Thiem, Grigor Dimitrov and David Goffin in Group Pete Sampras.