Murray battles past Nishikori

Andy Murray fought back to beat Kei Nishikori in an epic contest and close in on a semifinal place at the ATP World Tour Finals.

The world number one lost a tie-break but came through 6-7 (9-11), 6-4, 6-4 against the Japanese fifth seed.

At three hours and 20 minutes it was the longest match since the event moved to London in 2009.

It is the first time since his debut in 2008 that the Briton has won his opening two group matches.

The victory, his 21st in succession, had added significance as Murray needs to at least match Novak Djokovic's results in London if he is to stay ahead of the Serb in the year-end rankings.

Djokovic has a 2-0 record in the Ivan Lendl Group, as does the Scot in the John McEnroe Group, having beaten Cilic in his first match.

Djokovic booked his place in the semifinals after an emotional 7-6 (8/6), 7-6 (7/5) victory over Milos Raonic on Tuesday.

Despite having a spiritual guru in his camp these days, Djokovic has been anything but serene lately and once again the defending champion cut an angst-ridden figure for long periods of a tense clash in the prestigious season-ending event at London's O2 Arena.

Djokovic handled everything a fired-up Raonic threw at him to ensure he remains on course to win the Tour Finals for a fifth successive year and record-equalling sixth time in total.