Andy Murray has suggested that his motivation to remain as world number one stems from needing to improve his game in order to stay above his rivals.
The Scot enjoyed an excellent 2016 which was capped off by becoming the sport's best player and winning the ATP World Tour Finals in London.
Murray is currently in Melbourne as he bids to win the Australian Open for the first time, and he has admitted that he will have to produce his best tennis to claim his fourth Grand Slam title.
The 29-year-old is quoted by BBC Sport as saying: "The reality is, in sport, that things obviously keep moving on, the game will get better.
"I'll obviously get older, the young guys will continue to improve, and also Novak [Djokovic], Roger Federer, Stan Wawrinka, Rafa Nadal and all the guys at the top are still going to be wanting to get there.
"I need to continue to improve. I for sure need to keep working hard."
Murray prepared for the tournament with an appearance in Doha, where he made the final before losing to Djokovic.