Rafael Nadal rallied to beat Nikolay Davydenko 5-7, 6-4, 6-4 on Saturday and set up a Masters Cup semifinal against top-ranked Roger Federer.
James Blake topped the Gold Group despite losing 6-2, 3-6, 7-5 to Tommy Robredo later Friday in the last round robin match.
Blake opened the season-ending championship with wins over No. 2 Nadal and No. 3 Davydenko and had secured a semifinal against defending champion David Nalbandian before the Robredo match.
He saved match points in the eighth and 10th games of the second set but ran out of luck when he pulled a forehand wide after Robredo earned his third match point with a clean backhand winner.
Nadal had more to play for against Davydenko, and took a while to get rolling.
Friday's win was "my best performance in a long time," Nadal said. "I won a very, very difficult match against the No. 3 in the world, and in his best performance.
"It was one of my best wins of the year."
He let Davydenko dictate from the baseline in the first set, using fast, flat ground strokes to work him side to side.
But Nadal varied his game in the second, using more slice and top spin and making Davydenko do the running.
Nadal is 6-2 overall against Federer, and the only player in the elite eight-man draw with a winning record against the Swiss star.