Andy Murray came from behind to defeat Kei Nishikori and move closer to the knockout stages of the ATP World Tour Finals.

The Scot recovered from losing the opening set on a tie break to clinch a 6-7 (9-11), 6-4, 6-4 victory in what was his longest three-set match of 2016.

An epic 85-minute first set saw Japanese star Nishikori come out on top to force the Wimbledon and Olympic champion to dig deep.

After trading breaks of serve, Murray was able to make his move at 4-4 to take the second set and force the match into a decider.

Murray appeared on the cusp of victory after racing into a 5-1 lead but his determined opponent held on to the end.

Victory for Marin Cilic against Stan Wawrinka in Wednesday evening's match would ensure Murray's progress to the semi-finals for the first time since 2012.