Andy Murray extended his winning streak to 21 matches with the defeat of Japan's Kei Nishikori. The victory puts the world number one on the brink of the semi-finals of the season-ending competition.
Andy Murray fought back from losing the first set to beat Kei Nishikori and edge closer to thre last four of the ATP World Tour Finals in London.
The world number one was pushed to his limits by Nishikori in the longest Tour Finals match played in the event's seven years at the O2 Arena, and the Japanese star made life difficult for Murray over the course of three hours and 20 minutes, eventually clinching the first set on a tie-break.
Murray, looking to keep his nose ahead of Novak Djokovic in the race to end 2016 as the world's top ranked player, was stirred into action.
It had taken 85 minutes to settle a gruelling first set, but Murray's energy levels remained high and he started the second set with an immediate break. Nishikori responded by levelling at four-all, only for Murray to break again and close out the set.
Even after more than two and half hours on court, Murray's notorious commitment to his fitness ensured he was still going strong in the final set and he broke in the third game.
Murray broke again, yet Nishikori didn't go quietly and he got one break back before the Scot at last aced one of his most demanding tests this year.
Murray is expected to reach the last four, but would go out if he loses to Stan Wawrinka on Friday and Nishikori beats Cilic.
Wawrinka keeps hopes alive
Reigning US Open champion Stan Wawrinka came through a testing contest with Marin Cilic 7-6 7-6 in the Wednesday evening session.
The Swiss won two tie breaks against the Croatian to record his first victory at this year's tournament, keeping his hopes alive in London.
Wawrinka, who lost his opening game to Kei Nishikori with a disappointing display, will now face Andy Murray on Friday, needing to beat the Scot to progress.