Del Potro battles to stay in contention

Juan Martin Del Potro has struggled to live up to his status as US Open champion in the two months since he won his first Grand Slam title, but the Argentine showed at London's O2 Arena yesterday that he is determined not to let his year fizzle out.

Del Potro's 6-4, 3-6, 7-6 victory over Fernando Verdasco was only his third win since Flushing Meadows but it kept alive his chances of qualifying for the semi-finals of the ATP World Tour Finals. In his final round-robin match tomorrow Del Potro will face Roger Federer in a rematch of their US Open final, when the world No 5 beat the Swiss for the first time in seven attempts.

The top two players in both four-man groups qualify for Saturday's semi-finals. Having lost to Andy Murray in his opening contest, Del Potro had to dig deep to win his second after Verdasco made a spirited comeback in the final set.

The Spaniard saved one match point when 5-2 down, hitting a crisp backhand cross-court winner after a lengthy rally, and another when trailing 5-4 as Del Potro netted a backhand. Nevertheless, all the world No 8's hard work was undone when he played a poor tie-break, which Del Potro won 7-1. Afterwards Del Potro revealed that the Manchester City striker, Carlos Tevez, a friend and fellow countryman, had given him a pep talk the previous night. Del Potro said: "He just told me: 'Try to win.' He may come to watch my match against Roger."

Del Potro has been whittling away at the gap between himself and Murray in the world rankings and could yet claim the Scot's No 4 spot by the end of this tournament, despite his poor results in recent weeks. Until yesterday Del Potro's only two victories since New York had come at the Paris Masters, when he beat the retiring Marat Safin and Fernando Gonzalez, who quit with an injury after two sets.