Andy Murray will hope to tighten his grip on the world number one ranking when he plays Marin Cilic at the ATP World Tour Finals on Monday.
The Briton, 29, will end the year at the top of the rankings if he wins the title at London's O2 Arena.
Murray faces Croatia's Cilic in his opening round-robin match at approximately 20:00 GMT.
"I just want to finish the year on a high note by playing well," the Scot told BBC Sport.
"If I finish number one, that's great, but that wasn't a goal of mine a few months ago.