Shanghai - Andy Murray rolled into the semi-finals in his debut week at the Masters Cup, defeating Frenchman Gilles Simon 6-4, 6-2 in a Red group showdown on Wednesday.

The Scot polished his record to a perfect 2-0 as he beat the last player to enter the eight-man field. Simon gained a place at the last minute when Rafael Nadal pulled out with a knee injury which will require a month or more to fully heal.

Roger Federer was fighting to stay in the chase later as the Swiss holder faced Radek Stepanek after losing an opening match to a Simon comeback effort on Monday.

Czech alternate Stepanek was inserted into the field when Andy Roddick withdrew just hours before the match with a turned ankle.

"In practise I just went over on it, we tried as much as we could to get it better," said Roddick. "I can't really stop and start very quickly. It's anything when I go kind of over on the outside it hurts.

"I do a lot of that a lot on my serve also, so it's definitely a tough prospect trying to beat Roger with no serve and not being able to move much.

"It's unfortunate for this event, but I don't think we're looking at anything more than a week or so," Roddick said.

Murray took a 4-0 lead in the first set against Simon, and had two points for 5-0 before the Frenchman went into recovery mode.

Murray lifted the first set as Simon pounded a backhand into the net, then went down a break in the third game of the second set.

Murray dominated from that point on to ease to victory in just over 90 minutes with his French opponent hampered by 37 unforced errors.

Murray improved to 3-1 over Simon, whom he also defeated in the Madrid Masters final last month. (dpa)