Roger Federer is an astonishing sportsman.
The tennis great is now 36-years-old, but despite his age, Federer continues to enjoy great success in the sport.
Going into 2017 many doubted that Federer could maintain his status as one of the world's best tennis players, but he proved his critics wrong by enjoying a tremendous year.
The Swiss had not won a major title since 2012, but he ended that barren spell by winning the Australian Open in January, before winning his second Grand Slam of the year at Wimbledon; taking his overall tally to an incredible nineteen.
As a result of his success, Federer climbed back up the rankings to second in the world and even managed to qualify for the ATP finals, making him the oldest player to qualify for the tournament since 1970.
FEDERER GETS OFF TO A GOOD START IN LONDON
Federer is searching for his seventh ATP finals triumph, and he got off to the perfect start with a 6-4 7-6 (7-4) against Jack Sock.
And after the match, The Swiss revealed he was happy with his performance. He said: "It was really just a matter of trying to keep the ball in play.
"The ball was flying, so after a while it was important to hit some good shots and play at a high intensity.
"I'm happy to have gone through. It feels wonderful to be back - I love playing at The O2. I can't wait for my next match on Tuesday."
FEDERER HAS HIS REGRETS
After Federer's match against Sock, Rafael Nadal was presented with a trophy for finishing the tennis season as the world number one.
And after his match, the 19-time major winner revealed that poor results in three tournaments prevented him from winning the trophy himself.
The eight-time Wimbledon champion said: "He was better throughout the year. He played more tournaments. He was incredibly successful throughout.
"He had more gas left in the tank than I did. I couldn't play as much as I've wanted.
"My only regret was I would have loved to be in contention through the Montreal finals, Cincinnati, U.S. Open.
"But things evaporated very quickly after he (Nadal) won the U.S. Open. That's when he made his final push.
"That was it for me really."
FEDERER ONCE AGAIN SHOWS HIS CLASS
And Federer once again showed his class by claiming that Nadal deserved the trophy.
He continued: "In some ways I'm happy he clinched it because he deserves it. And like this, I can focus on playing the tournament, and not having to talk about that at the same time.
"Sure, I would have loved to be it, but you can't be it with that many tournaments, so it's no problem for me."