Andy Murray’s hard work in reaching the ATP World Tour Finals was significantly undone by a poor display in losing his opening match to Kei Nishikori.

Murray played six weeks in a row, winning three tournaments, to book his spot at the eight-man event in London, but the odds are now firmly against him progressing from the group.

The Scot’s 6-4 6-4 defeat by debutant Nishikori means he will almost certainly need to beat the other two players in Group B, Roger Federer and Milos Raonic, to reach the semi-finals.

Even that might not be enough, with a straight-sets loss leaving him vulnerable when the final round-robin calculations are made.

Murray (27), who had not dropped a set in three matches against Nishikori, won only 26 per cent of points on his second serve.