James Blake booked his place in the Masters Cup semi-finals with a three-sets win over Nikolay Davydenko.
Blake beat Rafael Nadal in his Masters Cup opener
The American eighth seed found himself a set down to the Russian third seed but Blake survived a break in the second set to win 2-6 6-4 7-5.
Blake's back-to-back wins over Rafael Nadal and Davydenko ensured he was the first of the Gold Group players into the last four in Shanghai.
Tommy Robredo's hopes were ended when he later lost to Nadal 6-7 (2-7) 2-6.
Davydenko must win his last match against Nadal on Friday to have a chance of going through.
"I'm just coming out here with nothing to lose, and trying to prove that I really do belong among these top players," said Blake.
"I like to think that I have by beating two of the top players in the world in consecutive matches.
"It's been an unbelievable experience and now that I'm in the position I'm in, hopefully my work here isn't done."
Nadal was still looking out of sorts in China and fellow Spaniard Robredo broke for a 4-2 lead in the opener.
The French Open champion responded immediately, breaking straight back and forcing the tie-break.
Nadal then raced to a 5-1 lead and claimed the first set in just over an hour.
The 20-year-old broke again early in the second and closed out the match - his first Masters Cup win - when Robredo hit his forehand long.
"I'm very happy with my first victory," Nadal said. "It was very important for me.
"I played more aggressively with my forehand, trying to play with more winners and I feel OK."
In the Red Group - with all four players still in contention - world number one Roger Federer will take on Croatia's Ivan Ljubicic on Thursday.
American Andy Roddick will face Argentine defending champion David Nalbandian having previously beaten him three times out of four.
Red Group: Roger Federer (Swi), Ivan Ljubicic (Cro), Andy Roddick (USA), David Nalbandian (Arg)
Gold Group: Rafael Nadal (Spa), Nikolay Davydenko (Rus), Tommy Robredo (Spa), James Blake (USA)