His body creaking after a stellar season, Novak Djokovic insisted on Saturday he is fit enough for a shot at his 11th title of the year.
The No. 1-ranked Djokovic withdrew from the Paris Masters quarterfinals last week with a shoulder injury that has blunted his late-season form.
He said he would be ready for his opening match at the season-ending ATP World Tour Finals against Tomas Berdych on Monday.
"I have been serving at 100 percent in the last two or three days," Djokovic said. "For me the shoulder is fine at this moment. I can say it is recovered and it is ready to compete."
Andy Murray and David Ferrer make up the rest of Djokovic's group, while Roger Federer, Rafael Nadal, Jo-Wilfried Tsonga and Mardy Fish compete in the other group starting Sunday.
Djokovic has already compiled what is widely regarded as one of the best seasons ever in men's tennis. He has a 69-4 record and has won 10 titles, including three Grand Slams. He went unbeaten until June in a run of 41 straight wins.
For the 19th and last tournament of a hectic year, Djokovic is back in London, the scene of his most precious win at Wimbledon.
"I was even thinking of going to Wimbledon for a cup of tea, as a member you know," he said. "It's the most prestigious, the most valuable event you can think of in our sport in my opinion and I think a lot of players would agree.
"That was the tournament I always dreamed of winning."
After Wimbledon, he went on to win the U.S. Open, beating Rafael Nadal, the player who started the year on top, for the sixth time in a final this season.
"It has been the best year of my career and I'm definitely proud of what I've achieved so far," Djokovic said. "But it's still not over and I have a very important event to be a part of and I try to do my best for the next week.
"Everybody wants to finish the season in great style."
Speaking on Friday, Rafael Nadal and Roger Federer both said it would be difficult for Djokovic to maintain such high standards in 2012, while Murray said Saturday that repeating a year like that "just doesn't happen in sport."
"It's like Barcelona in football," Murray said. "It's the best team but to win back to back Champions Leagues, even though you're the best team, it's so tough, the margins are so small. A lot of things have to go your way."
Djokovic vowed not to rest on his laurels.
"It's always possible to get better," he said. "I like to think of my game as a complete game but I think I still have room for improvement."
However, Djokovic accepted Federer's concern that staying at the pinnacle of the sport presents a whole new challenge because of "all the other things you have to do that go with being world No. 1."
"I know it's going to be really tough," Djokovic said. "I know with the new position I have, I have more expectation, more responsibility, but I'm ready for it.
"Everything I do in my life it's a challenge."