Fifth seed Tomas Berdych kept his Paris Masters challenge on course after rallying from a set down to beat Kevin Anderson on Thursday.
The Czech world number six, a champion at the event back in 2005, overcame a sluggish start to book a quarter-final date with France's Gilles Simon.
Berdych improved his head-to-head record against big-serving Anderson to 4-0 with a 1-6 6-3 6-4 triumph and has now won nine matches this season after losing the first set.
He will play home favourite Simon for a place in the semi-finals after Kei Nishikori withdrew from his scheduled third round match with the Frenchman due to a recurrence of an ankle injury.
Nishikori, seeded 15th, beat Benoit Paire in the opening round earlier this week but said the problem, which he has been struggling with since Shanghai last month, had worsened after his return to action.
"I tried to play here but after the first match the pain became worse," Nishikori said.
"It hurt last night when I was back at the hotel. I tried to warm up but I wasn't at 100 percent."
