Montreal, Aug 17 (DPA) Andy Murray used superior fitness to triumph in a heated two and three-quarter-hour struggle over Argentine Juan Del Potro to win the Montreal Masters title 6-7 (4-7), 7-6 (7-3), 6-1.

Sunday's victory makes the prefect start for Murray, who will take over from Rafael Nadal on Monday as second in the world behind Roger Federer.

Murray now owns five titles this season, level alongside Nadal on ATP trophy honours. He heads to Cincinnati next week for a title defence at that Masters event.

The 22-year-old was out in a fortnight of training in sub-tropical Miami in the weeks leading up to the Montreal start.

Murray said that three aces in the second-set tiebreaker against world number six Del Potro, winner of the Washington title last weekend, got him back in contention after losing the 62-minute first set in a decider.

World No.6 Del Potro, who took treatment on his left shoulder and rib and went off court before the start of the third, looked to have exhausted his energies at the end.

Murray finished with 16 aces and broke the South American four times.

He now stands 4-1 in the series after losing his only match to Del Potro at Madrid on clay three months ago, beating the Argentine in all three of their hardcourt matches.