LONDON (AP) - When Roger Federer looks around at his opponents for the ATP World Tour Finals title, there are seven familiar faces looking back.
A bit too familiar perhaps, for someone who is running out of new challenges in a record-breaking career.
With the season-ending tournament starting Sunday with only one newcomer in the field, Federer is among those wondering when the next great tennis talent will come along to shake up the world rankings.
So far, he sees no credible candidates.
"Promising newcomers? Not a whole lot, really," Federer said, summing up the lack of young talent. "I was asking myself the question too, why don't we have any teenagers in the top 100?"
That used to be quite commonplace in tennis, even in the top 10. Now though, Andy Murray and Novak Djokovic at age 23 are the two youngest players to qualify for the eight-player London tournament.
Tomas Berdych, this year's Wimbledon runner-up, is making his debut at 25, while Federer is the oldest at 29 in his ninth straight appearance. Andy Roddick and David Ferrer are both 28, while Robin Soderling is 26 and top-ranked Rafael Nadal is 24 _ and qualified for the sixth straight year.
"It's quite surprising for me, because when I was coming up there was (Lleyton) Hewitt and (Marat) Safin and Roddick and (Juan Carlos) Ferrero and Tommy Haas, they were all excellent players and in the top 100 as teenagers," Federer said. "It was normal, and on the women's side it was even more extreme.
"But maybe the game has become more physical and more mental, and that's why maybe players today need a bit more time to break through."
Indeed, many players seem to reach their potential in their mid-20s these days. Berdych had his breakthrough when he stunned Federer in the Wimbledon quarterfinals this year before losing to Nadal in his first Grand Slam final.
Soderling made a similar splash by beating Nadal at the 2009 French Open, before going down to Federer in the final. This year, he beat Federer in the quarterfinals before losing to Nadal in the title match.
Roddick, for one, isn't surprised by the slower developments.
"No, if you look at the way the game has changed, and how physically demanding it is now," Roddick said. "I weigh 20-25 pounds more than I did when I started out. But the game wasn't as physical, the conditions were a little faster.
"I think you had to rely a little less on your body when I was coming up, frankly. So I think it's a tough ask of a 17, 18-year-old to do it for 40 weeks a year. I think that's almost the main example that you can point to as far as what's changed."
And it may explain why the field at the ATP finals hasn't changed much.
Six of this year's players qualified last year as well, although Roddick had to sit out with an injury.
"It's a tough thing to do, not that many players have been able to break through and make it for the first time," Murray said. "It shows you've had a good year."
Last year's champion Nikolay Davydenko missed out this year after struggling with injuries and falling to No. 22 in the rankings. The 2009 runner-up Juan Martin Del Potro has missed most of the year after wrist surgery.
The tournament begins with a round-robin group stage, meaning every player is guaranteed three matches. Murray plays Soderling in the first match Sunday, before Federer takes on Ferrer. The other group starts play Monday.
Federer is looking for his fifth title in the event, and said he's hoping to end the year on a high.
"I feel like I've got one more tournament left in me," Federer said. "My body is not screaming for a vacation quite yet. ... This is a huge tournament for me. It's a goal for the entire season, trying to make it here. And once you make it here, trying to beat the fellow top-10 players, which is always fun to play against and face off at the end of the season. And you hope you can save the best for last."
There's also the hope that by this time next year, there may be some more new faces at the tournament. "I'm excited too to see what's coming up next," Federer said.
Notes: Nadal has won the ATP tour's Stefan Edberg Sportsmanship Award for the first time, ending Federer's streak of six in a row. Nadal earned the award, which is voted on by tour players, after winning three Grand Slam tournaments in 2010.