Gaston Gaudio made a successful fightback from one set down to beat Chile's Fernando Gonzalez in full sets on Friday, edging the replacer for Andre Agassi on sets difference to make through to the semifinals at the ATP tennis Masters Cup.

Winning on just one ace and 26 winners against Gonzalez's 13 aces and 44 winners, the seven-seeded Gaudio was taken two hours and nine minutes to wrap up the coming back Gold Group victory.

It's the fourth time for the 26-year-old Argentine to defeat the Chilean in as many their encounters, two of which Gaudio won on clay courts this year. Before Friday's matchup at the 4.45 million US dollars season-ending event, Gaudio has yet to drop a set to Gonzalez.

With the victory, Gaudio came out the last masters making to the semis, joining world number one Roger Federer, top Russian Nikolay Davydenko and fellow Argentine David Nalbandian in the last four who qualified with top two finish in each group.

Gonzalez, ranked 13th in the world, could have been the one more confident Friday, after he entered the elite eight-man field of the year-ending tournament for Agassi's pulling out due to injury and opened his own campaign on a victory over second seed Rafael Nadal' s replacer Mariano Puerta on Wednesday.

"I have a lot of confidence that I can beat any player. If I have one more match, it will be perfect for me. But I was an alternate and I have to play what I have only," said the Chilean.

Opening Friday's match against the disconcentrated Gaudio with ease, Gonzalez soon took the first set to victory on 6-1 with cracking 4 aces, 13 winners against 4 unforced errors.

The 25-year-old should have end up the match in short when leading 5-4 in the second set and holding two match points. But Gonzalez seemed too anxious to hold his nerve, wasting a third match point before succumbing the game to the serving Gaudio.

Gonzalez then lost his way for following match, double-faulted to grant his Argentine opponent a late break in the third set which set the tune of the game.

"I was dominating during the first two sets. I was serving really good. I was feeling the ball unbelievable, and I was hitting every shot how I want," he said.

"But I think it wasn't an error, because I played a bad game when I served for the match. I only put one first serve in, and then I lost that game," he added.

"And in the following game, I had three match points. But you never know when the other guy is serving. It's a little bit of bad luck and a little bit that I didn't play good in that game."