Rising Japanese star Kei Nishikori puts Andy Murray back on his heels In charge: Kei Nishikori was able to dictate terms against Andy Murray, who he had not beaten in three previous attempts. Andy Murray admits he faces a challenge to advance past the round-robin stage of the ATP World Tour Finals after a poor opening against Kei Nishikori, the rising Japanese star who has had a more profound light-bulb moment of his own. The world No. 5 is no longer so reverential towards the grand slam champions he once idolised: notably Roger Federer, who he plays next. Federer, the 17-time major winner, is group B's other unbeaten player after a 6-1, 7-6 (7-0) win against Canadian seventh seed Milos Raonic. Earlier on Sunday, Murray, the Olympic and dual grand slam champion, became Nishikori's 10th top-10 victim this season, which is more than he managed in his previous six seasons. Yet personal bests also double as national/continental records for Nishikori, the groundbreaking US Open finalist who has acknowledged he was motivated by the achievements of female Asian trailblazer Li Na, and saddened by her recent retirement. Timely, then, that the US-based 24-year-old is no longer just aspiring to greatness, but heading impressively towards it. The latest first for Nishikori came when he celebrated his debut qualification for the ATP's season finale by pooping the party of Britain's great - and in-form - hope, 6-4, 6-4. Murray had worked so hard to reach the $7.5 million tournament after an initially difficult return from back surgery that perhaps, by the time he walked out in front of the packed house at the 02, the effort had begun to tell. Or maybe he underestimated Nishikori, a fine shotmaker and superb mover who dictated terms against the 2013 Wimbledon champion, hit more winners and fewer errors, at least matched Murray for groundstroke velocity, and reduced him to just a 27 per cent success rate on second-serve points. The result could well be decisive, for if sets-won count in the eventual semi-final calculations. Murray, a three-time visitor to the last four, is starting from 0-2 down. "It's harder to qualify when you lose your first match - that's pretty obvious," said the Scottish fifth seed. But unlike the other events you still have a chance to go through. If this were anywhere else, I would be out of the tournament. You need to try to forget about today, work on some things tomorrow, and hopefully play better on Tuesday ... I need to win my next two matches more than likely, and win them well if I want to go through. I'm definitely going to have to play better if I want to get through. Nishikori is playing just like he would like to be, surprising even himself with the way he overcame some early tension in front of a full house. He looked around, but not up. Too many people up there, apparently. Big stadium. Big nerves. "But same time I was really excited to play with this crowd," said Nishikori, who could not speak a word of English when he moved to Florida to train when he was 13. You know, I was thinking, 'very honoured to be here'. First time to be top‑eight player. I was really happy that I played good tennis on this situation. I knew I was going to get little bit tight because this is my first opportunity here. And playing Andy, I never beat him before. But I was little bit surprised at how I played on the court, very confident. Very looking forward to play next match. That means Federer, with whom he shares a 2-2 record, having overcome the desire to genuflect to the player he admires above all others. "After turning pro, I was feeling a lot of respect to everybody actually, especially top players," Nishikori said. Like first time I play Roger, couldn't play anything because I respect too much. I wasn't go for win actually. I was just ... playing tennis against my idol. That was one of the problem I had. But after couple years I got, I don't know, mentally strong. I have to be strong to beat them. Maybe that's one of the reason we Asia players has to be really strong. You have to believe yourself. Murray witnessed the benefits first-hand and, despite his own frustrations, was generous with his praise for an opponent he had beaten in all three of the pair's previous encounters. The Scot does not believe Nishikori has improved his technique so much as his belief he can win. He's playing with more confidence. Because of that, he's able to take more chances and be a little bit more aggressive than he was previously," said Murray, who next plays Raonic. But he's always been a tough guy to play against because from the back of the court he's able to take the ball early. He can change direction of the ball. He's got a lot of talent in his hand. Even when you get the ball in difficult spots on the court, he's a good shotmaker. He's always been able to do that, but with the confidence he's a bit more consistent throughout the course of the match as well. Linda Pearce is a guest of the Barclays ATP World Tour Finals.