Andy Murray believes 'still has chance' at ATP Tour Finals despite losing to Kei Nishikori in opener

British number one Andy Murray believes that he still has a chance to go through the ATP World Tour Finals despite making a disappointing start to the tournament in London with a straight-sets loss to Japan's Kei Nishikori.

The Briton fought back from 4-1 down in the second set to level, but Nishikori broke serve for a fourth time to win 6-4, 6-4. Murray faces a tough task to claim one of the two semifinal places from Group B as six-time champion Roger Federer beat in-form Milos Raonic.

Murray would face Raonic in Tuesday's evening session, the Canadian having lost to Federer on Sunday.

After an exhausting six-week schedule that saw him play 23 matches and win three titles to earn his place in London, Murray could not carry that form into his opening match as world number five Nishikori overcame a nervous start on his ATP Finals debut and built the pressure on Murray, who made 28 errors and won just 27percent of points on his second serve, The BBC reported.

Murray admitted that he didn't serve well enough, before conceding that Nishikori was able to dictate a lot of points, especially behind his second serve.

Murray had been given a warm reception from the O2 Arena crowd on his first appearance in the UK since Wimbledon, and the Scot looked well set after Nishikori double-faulted to drop serve at 3-2.

The match then shifted momentum dramatically and ultimately proved decisive in a desperate service game from Murray.

Murray said that it's harder to qualify when one loses ones first match, that's pretty obvious, but added that unlike the other events, one still has a chance to go through, before admitting that if this were anywhere else, he would be out of the tournament.