Andy Murray made home advantage count as he edged a topsy-turvy clash with US Open champion Juan Martin del Potro 6-3 3-6 6-2 in the opening singles match of the Barclays ATP World Tour Finals at London's O2 Arena.
The British number one is competing at the prestigious eight-man event for the second time after reaching the semi-finals on his debut in Shanghai last year and dug deep to get his Group A campaign off to the perfect start.
Del Potro, who was won only two matches since his New York triumph in September, put in a very inconsistent display, with some scorching winners punctuated by simple errors.
The first set was a strange affair, Murray saving two break points in the opening game before going on to take a 5-0 lead.
Del Potro took a medical time-out after the third game to receive treatment to his face, but he was certainly struggling to find his range and some basic errors left the Scot barely able to believe his luck.
It was almost inevitable Del Potro's malaise would not last and, having saved two set points to avoid a whitewash, he retrieved one of the breaks before Murray finally clinched the opener at the eighth time of asking.
The Scot had won four of their previous five matches but the clashes have often been close and he would have expected the Argentinian to come out firing in the second set.
And that is exactly what transpired, a sloppy Murray service game allowing Del Potro to break to love then open up a 3-0 lead.
Murray broke back but soon dropped his serve again and Del Potro went on to level the match.
The home favourite was certainly not at his best and seemed to be struggling for rhythm, understandably so given the pattern of the match.
He recovered from 15-30 to hold serve in the opening game of the decider and finally got the crowd really behind him when he capitalised on a second break point to move into a 2-0 lead.
Del Potro rallied in the fourth game and then put his opponent under pressure with some more huge groundstrokes but Murray served well and sealed victory with a backhand winner after Del Potro had put himself in trouble with successive double faults.
Murray said: "It was always going to be tough. I played well today, started really good, he came back into it but I stayed tough in the third set."