Novak Djokovic believes a lack of court sharpness led to his defeat to year-end world number one Andy Murray in the final of the ATP World Tour Finals. The Serbian seemed out-of-sorts as he slumped to a 3-6 4-6 defeat to Murray, who won his maiden title at the season-ending tour finals.

The defeat concludes a second half to the season during which the 29-year-old has failed to win a tournament - a period which Murray has taken full advantage of. The Briton strung together a career-best 24 wins in a row, which included claiming five titles consecutively to leapfrog the 12-time major champion in the men's rankings.

Since winning the French Open to become the eighth player to complete the career grand slam, Djokovic suffered early exits from Wimbledon and the Rio 2016 Olympic Games, before failing to win the US Open in the final against Stanislas Wawrinka.

But with Murray having enjoyed a stellar run into the year-ending tour championships, Djokovic admits he might have been short of time on court.

"Maybe in the decisive moments today I lacked that, I guess, match play, match situations that I didn't have too much in the last couple of months," he told reporters, after failing in attempts to win a record-equalling sixth title at The O2 Arena.

"On the other side, he played a lot of matches, especially in the last couple of months, and he won them all. He's on a streak.

"I guess even though he has had very long matches, especially the one yesterday [three hours and 38 minutes against Milos Raonic], people were thinking maybe he's going to be slightly tired, but he didn't seem so.

"More than anything, he felt comfortable in the rallies and exactly knew what to do. On the other hand, I hesitated, and it didn't work."

Despite a harrowing season half to the 2016 season, Djokovic remains content with his achievements, in which he won a record equalling sixth Australian Open, completed the career-grand slam at Roland Garros and stretched his spell as world number one to 122 weeks.

"As I said, many highlights, many things to reflect on and be proud of," he added. "The French Open is definitely on top of that list. I've had better seasons results-wise. But every year is an evolution for me. It's a different year. I mean, it's hard to expect to repeat all these things forever. I mean, nothing is eternal. I know there are other players coming up, present players that are getting stronger. I'm trying to do the same thing. Sometimes it works. Sometimes it doesn't."