John Isner and Jack Sock remain in the hunt for the final spot at the ATP Finals by beating Juan Martin del Potro and Fernando Verdasco in their respective Paris Masters quarter-final.
The American duo need to win the tournament to reach the finals in London this month.
Isner, the ninth seed, overcame Argentine 13th seed Del Potro 6-4 6-7 (5-7) 6-4.
"I've given myself a pretty good shot to qualify," Isner said.
"But it's going to be very tough."
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The loss ended Del Potro's hopes of qualifying for London's elite eight-man field.
"I'm exhausted but I did all my effort, I don't have anything to (reproach) myself (for)," Del Potro said.
The eighth and last berth for London is between Isner, Sock and Pablo Carreno Busta of Spain, who is ahead in the race.
Isner will face Serbian qualifier Filip Krajinovic next after he advanced when top-ranked Rafael Nadal pulled out of their encounter with a right knee injury.
"I'm going to do my treatment, do my best to be playing in London," Nadal said.
"But I cannot talk about that now; it is tough enough for me to pull out from here."
Krajinovic, ranked 77, is through to his first Masters semi-final and is the first qualifier to reach the last four in Paris since Jerzy Janowicz in 2012.
Meanwhile, unseeded Julien Benneteau continued his unexpected march by knocking out third-seeded Croatian Marin Cilic 7-6 (7-5) 7-5.
He sealed victory on his first match point, breaking Cilic's serve with a cross-court forehand winner.
"I was looking at my brother, who is my coach, and at my wife; I am so happy to make her proud," an emotional Benneteau said.
"It's an indescribable joy."
In his last Paris Masters before retiring, the Frenchman has a shot at a first career title on home court.
He will face 16th-seeded Sock who accounted for Fernando Verdasco 6-7 (3-7) 6-2 6-3.
Sock needed five match points before he finally tamed the Spanish veteran in a late-night thriller that finished about 1am.
