World number one Rafael Nadal says his knee is “not perfect” but expects to be fit enough to start the ATP World Tour Finals in London on Monday.
The Spaniard, 31, withdrew before his quarter-final match in last week’s Paris Masters with the injury.
Nadal will play Belgium’s David Goffin in his opening tie.
“If I didn’t believe I could be ready for Monday I wouldn’t be here,” said Nadal, who has won the US Open and the French Open in 2017.
Nadal, who has already guaranteed top spot in the world rankings at the end of the season, also faces Dominic Thiem of Austria and Bulgarian Grigor Dimitrov in his group.
“The knee is not perfect, of course, after having to retire from Paris,” Nadal told BBC Sport.
“In a couple of days you cannot expect to be 100% but I had treatment and I’m expecting to be better and better every day. I’m here to try my best to give me a chance.”
World number two Roger Federer, 36, opted not to play in Paris, after beating Argentine Juan Martin del Potro to win the Swiss Indoors in Basel last month.
The Swiss 19-time Grand Slam champion has won seven titles in 2017, including Wimbledon and the Australian Open, and played a charity event against Britain’s Andy Murray in Glasgow on Tuesday.
“I feel fine,” said Federer, who opens his campaign on Sunday afternoon against American Jack Sock.
“I had a very slow last 10 days. I practised twice during the week in Paris and I only hit for an hour both times.
“I came here on Monday, then played the exhibition against Andy [Murray] in Glasgow and was then off again on Wednesday so I’ve been really taking it slowly to really just make sure I totally rested after Basel.”