Losing concentration for a moment, Federer was broken twice anddown 5-0 in the second set before wrapping up the match 6-0, 2-6, 6-2 in one hour and 25 minutes.

Roger Federer of Switzerland returns a shot to Guillermo Coria of Argentina.(Xinhua) This match decided little in terms of the end result at the 4.45 million US dollars event of men's professional tennis, as Federer has already qualified for the semifinals with two group wins and Coria is definitely out after losing both of his former matches in Red.

However, there is still the small matter of pride and dollars at stake, since Federer was trying to preserve his unbeaten run atthis tournament while chasing his third consecutive year-ending title.

The superlative Swiss, 24, should have made short work of Coriawhen the 23-year-old called his physician onto the court to treat on his left ankle, which halted the play for more than three minutes during the first set.

"I really felt at some point I wanted to leave the court. I wanted to stop playing," said Coria."For respect that I have forRoger Federer, that he's an unbelievable player, No. 1 in the world, and for the fans, I felt that I had to give all my best.

"It's the last match of the season. As I say, for the respectsthat I have for the fans and for Roger,...I had to stay and continue playing."

Federer cracked 29 winners throughout the match against 33 unforced errors including 16 ones in his surprisingly struggling second set. Guillermo Coria of Argentina reacts after missing a shot during the match against Roger Federer.(Xinhua)

"I got off to a bad start," commented Federer."I figured if Iwould have kept on to of things, the result would have been very different. But, you know, that's how it goes. In the end, I'm happy I didn't use too much energy and came through. That's what counts.

"But obviously, I'm disappointed I couldn't do better in the second."

The two-time defending champion had kept in low as he was pulled into deciders in his Red Group opener against 12th-ranked David Nalbandian on Sunday and was even forced tiebreaker when facing the world No. 7 Ivan Ljubicic on Tuesday.

With Thursday's victory, Federer again saved his near-perfect record at the Tennis Masters Cup, and extended his season-best match record to 80-3.

He has built upon an imposing 15-1 record at the Masters Cup, with his only loss came to Lleyton Hewitt in the Shanghai 2002 semifinals.

The Shanghai match was the first in six weeks for Switzerland'sFederer, who has already clinched the world No. 1 year-end rankingfor the second year in succession. He last competed in Bangkok, winning his 11th title of the season on October 2.

After American veteran Andre Agassi and second seed Rafael Nadal pulled out due to injuries on Monday, the Swiss has been left the only top-five player in the elite field.

Federer overcame the effects of the ankle ligament injury scarewhich threatened to keep him off the court at the Qi Zhong tennis center.

"I'm not at a hundred percent fitness-wise because I couldn't get the practice in I needed on court with tennis or running on the running machine or being able to lift weights. This is maybe why I'm struggling a little bit," he added.

"Again it's definitely going to get through this tournament. It's only two matches left at the most.

"But so far this season I never really had condition problems throughout the match. This is because of the injury I'm not at a hundred percent. I'm not really too worried about it for the weekend." Enditem