Murray knew he would have been eliminated from the prestigious season-ending event at London's O2 Arena if he lost to Canada's Raonic, but the world number six produced a strong performance to secure his first Group B win and remain in the hunt for a last four berth.

The former Wimbledon champion now has to beat six-time winner Roger Federer in his final group match on Thursday to qualify, while Raonic, having lost both matches, is almost certain to be knocked out.

"On Sunday, there wasn't much magic. Today I came up with some good shots in the right moments. Milos didn't serve as well as he can and that helped," Murray said.

"It's a nice match against Roger to look forward to. It'll be a great atmosphere again."

Murray's victory also meant Federer is not 100 percent certain to make the semis despite winning both his group matches, including a 6-3, 6-2 stroll against Japan's Kei Nishikori earlier on Tuesday.

After playing for six consecutive weeks in a successful bid to qualify for the Finals after briefly falling out of the top 10, Murray chalked up titles in Shenzhen, Vienna and Valencia to salvage his ranking.

Yet he looked totally devoid of inspiration and energy in his lacklustre loss against Nishikori on Sunday.

Murray knew he had to improve dramatically against Raonic, who had won three of their four previous meetings.

Raonic had hit 1,103 aces this year and he tried to send a statement of intent with a venomous 138mph ace in his first service game.

Murray wasn't intimidated by the early barrage and carried the fight back to the world number eight, earning two break points in the fourth game.

 - Forehand errors -

Although Raonic got out of trouble on that occasion, he wasn't landing enough first serves in to keep Murray on the back foot and the Scot, taking advantage of a series of forehand errors from his opponent, eventually broke for a 4-2 lead.

That proved decisive as Murray closed out the first set and he kept up the pressure in the second.

Raonic seemed to be cruising at 40-0 in the third game, but the Canadian's double-fault gifted Murray a break point which he converted with a superb crosscourt return.

Murray's concentration wavered then and he allowed Raonic to break back with a sloppy service game.

But he was still reading Raonic's serve well and landed the knockout blow with a break in the 11th game before serving out the win.

At 33, Federer is the oldest player to qualify for the Tour Finals in his 13th consecutive appearance, but he has been in age-defying form over the last three days.

The 17-time Grand Slam champion has defeated Raonic and US Open finalist Nishikori without dropping a set and will guarantee top spot in the group, which would bring the added bonus of likely avoiding a semi-final showdown with Novak Djokovic, if he beats Murray.

Federer, who last won the Tour Finals in 2011, didn't need to be at his very best against Nishikori, who made 30 unforced errors in a sloppy effort that left him with one win from two matches.

"I've know Kei since he was 17 years old and always thought he was a great talent. He's going to have a great future so I'm very pleased with the way I played," Federer said.

Nishikori needed treatment on his right wrist during the match, but he hopes to be fit to face Raonic.

"It was just a little bit of soreness. I have one more day off, so I will try to recover well and hopefully I can win the next one," he said.

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