Novak Djokovic believes 2015 has been his best year in tennis and hopes to continue it at the ATP World Tour Finals.
The Serbian has won three grand slam tournaments and six ATP World Tour Masters 1000 events this season, with his record standing at 78-5.
He has been drawn against Roger Federer, Tomas Berdych and Kei Nishikori for the tournament in London and is looking forward to the challenge.
"I've had by the far the most successful season of my life and I'll try from my side to keep going," Djokovic said at the draw. "Of course it's not going to be easy, this is the greatest challenge you can have outside of the grand slams.
"For tournaments like this the bottom line is we all love the sport we have great passion to compete.
"It's been a long season, so this is a crown for the achievements of all these players.
"We are all excited to get it going and be part of a great, very successful event."
Federer acknowledged that being drawn against the world number one makes things difficult but is keen to get out on the court.
"The groups were always going to be tough, regardless of who was going to be in it," he said.
"I'm excited to be back and can't wait for it to start.
"In practice, so far so good, but that's not where you're going to win."