
The elite eight at the World Tour Finals —
Roger Federer, left, and Novak Djokovic, right, headlined the World Tour Finals in London, but the Swiss star had to pull out of the final due to a back injury. The year-end championships featured eight of the world's best tennis players.

The elite eight at the World Tour Finals —
Djokovic's finest moment this year came when he won a second Wimbledon title by defeating Federer in an absorbing five-set match. He's the two-time defending champion at the World Tour Finals.

The elite eight at the World Tour Finals —
Federer is making his 13th consecutive appearance at the event. He rebounded this season after a bad back hindered his 2013.

The elite eight at the World Tour Finals —
But will Federer be fully focused in London? He'll lead Switzerland in the Davis Cup final in late November. The Davis Cup is one of the few prizes in tennis Federer hasn't won.

The elite eight at the World Tour Finals —
Federer's countryman, Stan Wawrinka, earned his London spot thanks largely to winning the Australian Open in January. But he's slumping entering the year-end championships.

The elite eight at the World Tour Finals —
Exciting Japanese baseliner Kei Nishikori became the first Asian man to contest a grand slam singles final when he reached the last stage of the U.S. Open. He has defeated both Djokovic and Federer in 2014.

The elite eight at the World Tour Finals —
Andy Murray desperately wanted to play at the year-end championships, competing for six straight weeks down the stretch. In the end he qualified -- and comfortably. Recovering from back surgery and splitting with coach Ivan Lendl made the first part of the year difficult for the Scot and 2013 Wimbledon champion.

The elite eight at the World Tour Finals —
Tomas Berdych is becoming a regular at the World Tour Finals. The always dangerous Czech reached the quarterfinals or better at three majors this year -- although given his weapons some would say he could do even better.

The elite eight at the World Tour Finals —
At the age of 23, Milos Raonic is already Canada's best ever men's singles player. Raonic made the semifinals at Wimbledon and last week beat Federer -- who downed him at the All England Club -- for the first time.

The elite eight at the World Tour Finals —
The third of three debutants in London, joining Nishikori and Raonic, Croatia's Marin Cilic didn't drop a set against Berdych, Federer and Nishikori as he won the U.S. Open in September. A year ago he served a drug suspension, which was subsequently shortened on appeal.