Merciless Murray off to flyer

Wimbledon it was not. Andy Murray and Juan Martin del Potro entered the O2 Arena for the first singles match at the Barclays ATP World Tour Finals with The Clash's "London Calling" blasting out over the PA system, while during the match video screens around the stadium proclaimed "ace" and "set point" at appropriate moments and music played during the changeovers.

The crowd of 17,467 – 2,500 more than the capacity on Centre Court at Wimbledon – was the biggest ever to watch a tennis match in Britain and they clearly enjoyed what they saw as the season-ending championships got off to the perfect start. Murray, the world No 4 and home favourite, beat Del Potro, the world No 5, 6-3, 3-6, 6-2 to put himself in pole position to qualify for the latter stages of the tournament.

Saturday's semi-finals will be contested by the two players with the best records in each of the round-robin groups. Roger Federer will be Murray's opponent tomorrow in the next round of matches in Group A after the Swiss recovered from a poor start to beat Fernando Verdasco in his first match. Murray beat Federer when they met in the round-robin stage of last year's event, knocking him out of the tournament, and has won six of their nine meetings.

The complicated maths of the format mean that tomorrow's winner may still have to win a third round-robin match to go through, although it is also possible to qualify with just one win in three matches.

Murray has been playing down his chances of winning here given his lack of recent competition, although he made a winning return earlier this month in the Valencia Open after a six-week lay-off with a wrist injury. Yesterday's match was his first against a top-five player since he lost to Federer in Cincinnati in August and his first win over such an opponent since April.

How much it meant was evident in Murray's celebrations. After cracking a backhand winner following a beautifully engineered rally on his third match point, the 22-year-old Scot leapt into the air in delight. "It was a really good start," he said afterwards.

Murray's bank manager will be similarly happy. Having picked up $120,000 (about £72,000) simply for turning up at the tournament, Murray pocketed the same again for this victory. Should he win the title without losing a match, he would take home $1.63m (nearly £1m), which is the biggest prize in tennis. Federer earned £850,000 for winning Wimbledon this year.

Although Murray said it was "a great atmosphere" inside the stadium, you had to wonder whether he was being diplomatic. For all the razzmatazz – the pre-match countdown alone must have lasted the equivalent of half a set – the atmosphere inside the stadium was generally muted.

For the most part the crowd were surprisingly subdued given that Murray was playing – and winning – in a tournament second only in importance to a Grand Slam event. It would have been hard to imagine any crowd anywhere else in the world being as quiet in such circumstances.

It was a match of wildly fluctuating fortunes. With Del Potro needing treatment after three games for a nose bleed – "I have a big nose," he said by way of explanation afterwards – the Argentine looked badly out of sorts and was soon trailing 5-0. Murray showed no mercy, combining subtle drop shots with some pounding ground strokes, although he needed seven set points to drive home his early advantage.

Del Potro, however, had started to piece his game together and by the time he had taken a 3-0 lead in the second set the US Open champion had won six games out of the previous seven. Serving more consistently and finding his range with his clubbing forehand, Del Potro levelled the match at one set apiece, having broken back immediately after Murray had recovered to trail 3-2.

The Argentine, however, has looked curiously fragile ever since his triumph in New York – he has won only two matches in the last two months – and Murray quickly took command of the decider.

Cutting out his errors and serving with greater accuracy, Murray took a 3-0 lead. At 2-5 down Del Potro saved two match points after serving two double faults from 15-15, but could do nothing about the third as Murray claimed his fifth victory in six meetings between the two men. Del Potro hit 31 winners to Murray's 30, though the more significant statistic was the Argentine's 38 unforced errors compared with the Scot's 26. "The start of the match was important," Murray said. "Me and Juan haven't played that much since the US Open. I kind of expected a little bit of a scrappy match, but after I went 5-0 up and he didn't start particularly well I thought the standard was very good. We played some great points and I'm obviously happy to get the win.

"I was happy with a lot of parts of my game. He has a big forehand. He can hit a lot of winners, but he can also make mistakes off of it. There was a period at the end of the first set until the beginning of the third where he was hitting it big. I managed to keep myself in the points with low slices and backhands up the line. They helped a lot to keep him out of that backhand court.

"He's got a big serve, a long reach and goes for huge shots. You just have to try and find a way through that. Tactically, I've always been quite good, so I found a way through it today."

Del Potro said that the nosebleed had not caused him any major difficulty. "Andy just started to play very hard and very well," he said. "He broke my serve very early, then he took control of the first set. My matches against Andy are always tough."