World number two Rafael Nadal recovered from a slow start to get his Masters Cup campaign back on track with a 7-6, 6-2 win over compatriot Tommy Robredo on Wednesday.
Nadal's victory meant that James Blake, who beat the Spaniard in his opening match, became the first player into the semi-finals after the American fought back to beat Nikolay Davydenko 2-6, 6-4, 7-5 in the other Gold Group match.
Robredo, who lost to Davydenko in his opener, cannot now qualify for the last four, while the world number three must win his last match against Nadal to have a chance of going through.
Nadal continued where he left off against Blake on Monday and sixth-ranked Robredo initially took advantage of his lacklustre display to break the French Open champion for a 4-2 lead.
That seemed to galvanise Nadal and he broke straight back but Robredo, who had lost all three of their three previous meetings, stuck doggedly to his task to force a tiebreak.
Nadal, however, played his best tennis of the day to race out to a 5-1 lead and found a superb down-the-line winner to claim the first set in just over an hour.
Another break early in the second set put Nadal on course for victory and although Robredo had three chances to break back, his fellow Spaniard saved them all to win his first Masters Cup tie on his fourth match point when his opponent went long.
American Blake, who lost his first five service games, rediscovered the mental resilience that got him past Nadal on Monday to come back from a set and a break down against Davydenko.
The 25-year-old New Yorker, playing in his first Masters Cup, first got his serve in order in the second set before ramping up the power to complete a remarkable turnaround against the tiring Russian.
"Once I started ... getting the momentum, I felt good," said the world number eight. "Obviously, he still could have won. A point here or there, he easily could have won that third set. I just felt like the momentum was in my favour, I was playing great."
Blake teed himself up for a fifth victory in five attempts against the Russian by lashing a beautiful return into the corner and won the match when Davydenko went wide on the next point.
Davydenko, aiming to reach the semi-finals for a second successive year, said he had not prepared well enough to take on the players from the top eight in the world over three sets.
"I was just losing power because I was losing concentration because I was ... very tired," said Davydenko, who blamed illness not his 31 previous tournaments this year for his fatigue.