Andy Murray takes on Canadian fourth seed Milos Raonic in the semi-finals of the ATP World Tour Finals on Saturday.
The Scot, 29, is trying to win the season-ending finale for the first time, and end the year as world number one.
He must at least match the performance of Serbia's Novak Djokovic to retain top ranking.
Five-time champion Djokovic takes on Japanese fifth seed Kei Nishikori in the second semi-final at 20:00 GMT.
- Murray v Raonic is live on BBC Two, BBC Radio 5 live sports extra and online at 14:00 GMT.