ATP World Tour Finals Venue: O2 Arena, London Dates: 21-28 November Coverage: One match each day live on BBC TV, streamed online & available through iPlayer; text commentary online and on mobiles for every singles match via BBC Sport website; every singles match live on 5live sports extra.
No retirement deadline for Federer
By Mike Henson
After seven years of making greatness routine, could 2011 be when Roger Federer slips back into the pack?
"In the past I've had an amazing run. I think I won 24 straight finals at one stage, so this could be the start of the streak again," he said.
If he does put together such a sequence, particularly if it includes reeling in runaway world number one Rafael Nadal, it would represent a compelling, and possibly conclusive, claim to be the greatest player ever.
"There's not a whole lot of promising newcomers. I was asking myself the question, why don't we have any teenagers in the top 100?"
Federer savours his Australian Open win over Andy Murray in January
"It is quite surprising to me because when I was coming up with Lleyton Hewitt, Marat Safin, Andy Roddick, Juan Carlos Ferrero, Tommy Haas, they were all excellent players and in the top 100 as teenagers."
The rankings offer little reassurance.
Whereas he began 2010 with a comfortable rankings lead, Federer ends the year staring up at Nadal, who lies almost two major victories clear and is likely to pull further ahead in early 2011.
Looking the other way, the decline from the top can be steep and swift.
Pete Sampras dropped from world number one for the final time at the age of 29 and was 12th in the world before he turned 30.
American legend John McEnroe won all seven of his major titles before the age of 26 while his great rival Bjorn Borg famously walked away from the sport at 25.
Bud Collins of the Boston Globe and Tennis Channel, has seen all these careers rise and fall in over 45 years commenting on the sport and believes the modern game is particularly unforgiving on ageing limbs.
But he also asserts that Federer is better prepared than most to last the course.
"Forget about 29 - Roger is a very young 29. The way he plays, with such smoothness and such balance, he is not getting hurt like everybody else," Collins told BBC Sport.
"With Nadal every shot is an explosion and with Federer many shots are lullabies.
It is going to be very difficult because Rafa is playing well
Federer on his chances of reclaiming top spot
"Nadal is really taking it out on his body, he is tremendously conditioned, but still the knees gave way and will the shoulder?"
"The most important word for Roger is motivation - how long does he want to stay at the top?"
But since Annacone, who previously worked with Sampras, was added to the team on a permanent basis in August, Federer has won in Stockholm and Basle and reached the final in Shanghai.
"That is the biggest signal that still he wants to improve," said Rene Stauffer, tennis correspondent for Zurich's Tages-Anzeiger and Sonntags-Zeitung, who has followed Federer since he was a 14-year-old rising star.
Annacone was given a full-time role after a month's trial with Federer
"I think it is a very smart decision, a fantastic choice.
"After two or three weeks I think the difference is already visible. Roger is already playing differently to how he was in the months before.
"If you look at him and the way he is talking about his game and talking about the tour and his ambition and you would have to think it would be the body that tells him not to play any more.
"He is still so enthusiastic and the fire is still burning in him."
That fire may not be enough to power him back to number one for the seven days needed to match Sampras' record of 286 weeks at the top.
Twenty-three players other than Federer have held that spot, but only four of them have been older than he is now when in possession of it and the Swiss admits he faces a tough task overhauling Nadal.
"Sure it is challenging. It is going to be very difficult because Rafa is playing well," said Federer.
"It's not something I have in mind right now. The goal is to play well here in London and prepare for next season and hopefully at some stage get it back.
"If not then I will focus on just winning tournaments. That is something I like doing as well!"
Sixteen majors attests to that, and, however he ranks against the rest, it may be a long time before a 17th can be ruled out.
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