Roger Federer saw his campaign to defend his Masters Cup title ended as he lost to Andy Murray in the last group match on Friday.

World number two Federer, who had to win the final round-robin match in the Gold Group to stay in the tournament, succumbed to his recurrent back injury and combative Murray 4-6, 7-6(3), 7-5.

That ensured Gilles Simon, who earlier beat Radek Stepanek, made the semis.

Murray will now face Nikolay Davydenko in the last four on Saturday, while Simon will play Novak Djokovic.

Friday's final group match was a unique experience for Murray, who went into the match knowing he did not need to win having already qualified.

It made little difference to the quality of play as both men came out firing in front of a packed crowd at the Qi Zhong Stadium.

With everything to play for, Federer took the initiative and got the first break in game four when Murray went long with a forehand.

The Scot responded immediately when an edgy Federer netted a backhand in the following game but he had to save three more break points in his next couple of service games as the champion kept up the pressure.

Finally, Federer made the decisive breakthrough in a superb 10th game, firing a beautiful backhand winner and a crunching cross-court forehand before Murray dumped a drop shot in the net at set point.

It did not appear to boost the champion's confidence though and he played a poor game to drop serve at the start of the second.

He handed Murray the break with two wayward forehands and soon slipped 5-2 down after a disastrous seventh game, with two double-faults and two dreadful volleys giving Murray the double-break.

Remarkably, it was the Briton who then suffered a shocking slump in form and he became increasingly angry as Federer wiped out the advantage, Murray double-faulting to bring the score level at 5-5.

Federer appeared in trouble when he slipped a mini-break down early in the tie-break and, despite winning the point of the match with a backhand smash, it was Murray who was in control throughout.

As the final set got under way, Federer twice had lengthy treatment from the trainer on his lower back - an area he had suffered problems with in the build-up to the tournament.

Murray duly broke serve early in the decider and Federer, moving gingerly between points, looked on the verge of spoiling his record of never having quit during a match.

But the Swiss was still able to play some magnificent strokes, in particular a killer drop shot and a sweeping backhand down the line in game five as he got the break back before incredibly moving ahead with a break at 4-3.

The drama was not over, however, as a pumped-up Murray got back on level terms yet again when Federer missed a regulation smash, to the astonishment of the 15,000 spectators.

Murray failed to convert any of seven match points in a fabulous 10th game but made no mistake two games later, sealing victory after three hours and one minute when Federer made an error.

Simon earlier completed his group matches with a 6-1, 6-4 victory over Radek Stepanek to finish with a record of two wins and one defeat in the Gold Group.

The Frenchman, ranked ninth in the world, only made it into the eight-man field when Rafael Nadal pulled out with an injury on the eve of the tournament.