MASTERS CUP, Shanghai: Dates: 9-16 November Starts: 0600/1000 GMT daily Coverage: Live on Sky Sports; live text commentaries on BBC Sport website; every match live on Radio 5 Live sports extra
Murray went into the match with a 4-2 record against Roddick
Andy Murray got off to a winning start at his first Masters Cup by defeating Andy Roddick in three sets in Shanghai.
The British number one came through 6-4 1-6 6-1 against the American in the season-ending event for the world's top eight players.
Murray still has round-robin matches to come against Frenchman Gilles Simon and world number two Roger Federer.
Simon caused a major shock by beating defending champion Federer 4-6 6-4 6-3 in the opening match in the Red Group.
The top two will go through to the last four, along with two from the Gold Group of Novak Djokovic, Nikolay Davydenko, Juan Martin del Potro and Jo-Wilfried Tsonga.
"The chances of me qualifying have gone up pretty significantly after I won my first match," Murray said.
"But in terms of winning it, there's a good chance I might still have to win two more matches to do that. But to qualify, it's probably going to be slightly easier than if I'd lost and if Federer had won."
Murray began in imperious fashion against Roddick, winning his first service game with three aces and a backhand winner before earning the first break with a cross-court forehand pass in game five.
The Scot served magnificently as he eased through the set without facing a break point, and a fifth win in eight meetings with Roddick looked inevitable.
But while Roddick is not the daunting opponent he once was, he remains a fighter, staving off a break point at the start of the second set to stay in the contest.
It proved vital because Murray then suffered an alarming slump, hitting two double faults in the next game as he dropped serve before appearing to conserve his energy for the decider as the set raced away from him.
Murray was breathing heavily as the third set began but his focus had returned.
In game two, Roddick saved two break points with an ace and a volley but could do nothing about a searing Murray backhand return on the third.
The Briton secured another break in game four, setting it up with a beautiful return at the feet of the incoming Roddick, before eventually serving out for a victory that leaves him well placed to reach the semi-finals.
Asked how he was feeling afterwards, Murray said: "Not great. He made it difficult and made me do a lot of running.
"It's tough to get over the jet lag. I've been going to bed at this time and hopefully I'll be better for the next match."
But Murray was pleased with his win despite his mid-match slump in form.
"I hit the ball well for most of the match, I just didn't serve well in the second set," he explained. "I had a chance to break him right at the start of the second, if I'd done that, then maybe the second set would have been a different story.
"I'm tired, but I felt like I played well. My legs don't quite have the snap in them that they did a few months ago."
Roddick was left bemused by the topsy-turvey nature of the match, adding: "The first and second set were actually pretty similar.
I'm tired, but I felt like I played well. My legs don't quite have the snap in them that they did a few months ago
"I thought he played a really good game to break me in the first set. I don't know if I missed a ball that game, I think he just came up with it.
"Then in the second, he gave one of his service games away and then I got the momentum. But he was able to establish (dominance) early in the third."
But the American was quick to praise Murray's patient tactics and his ability to beat him at the net.
"He's very good at taking pace off," the world number six explained. "I think more so than his returns, it's just his ability to pass off of good approach shots, I think that's the biggest thing.
"Even if you hit a good approach shot, a lot of times he's able to come up with something, which makes it tough."
Murray's next match is against Simon on Wednesday and he will face Federer on Friday.
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