Andy Murray hopes to recover from his epic win over Kei Nishikori in time to face Stan Wawrinka at the ATP World Tour Finals on Friday.
The Briton, 29, needed a tournament-record three hours and 20 minutes to see off Nishikori on Wednesday.
He returns to London's O2 Arena 48 hours later knowing he must take a set off Wawrinka to ensure a semi-final place.
Murray will play the Swiss third seed at 14:00 GMT on Friday.
- The match will be live on BBC Two, online and Radio 5 live sports extra.