Roger Federer got his quest for a fifth Masters Cup title off to the worst possible start with a 4-6 6-4 6-3 defeat at the hands of Frenchman Gilles Simon on Monday.

The Swiss top seed, who withdrew from the Paris Masters 11 days ago with a back injury, made 50 unforced errors to fall to a second defeat in two encounters with the 23-year-old world number nine.

"The better you play, the better he plays, he's quite an unusual player and he makes you work hard and runs very well," said the world number two, who also lost to Simon at the Toronto Masters in July. "Definitely today I missed shots I normally don't miss. I think that's just lack of practice.

"It's the only tournament where I really have a chance after losing the first match so I'm happy it happened here."

Third seed Andy Murray blew hot and cold on his Masters Cup debut, prevailing 6-4 1-6 6-1 over Andy Roddick in the other match in the Red Group, from which two players will qualify for Saturday's semi-finals.

The 21-year-old Briton rattled off three aces in his first service game on his way to wrapping up the first set but effectively forfeited the second to his American rival with a series of unforced errors.

The deciding set was equally one-sided and Murray took just 25 minutes to dispatch the fifth seed, clinching victory with a leaping backhand volley.

"I'm tired," Murray said. "I felt like I played well. You know the legs don't quite have the snap in them that they did a few months ago.

... contd.