World No 8 Robin Soderling, the highest-ranked player left in the Barcelona Open after a slew of withdrawals, sprinted into the quarter-finals with a 6-3, 6-2 win over Spain's Feliciano Lopez on Thursday.
The second-seeded Swede, last year's French Open runner-up, next plays Argentine Eduardo Schwank who put out Spain's Ivan Navarro 6-3, 7-6.
Third seed Jo-Wilfried Tsonga and number five Fernando Verdasco had to come from behind to advance.
Frenchman Tsonga overcame Spain's Nicolas Almagro 5-7, 6-1, 6-4 while home hope Verdasco beat Austrian Juergen Melzer 3-6, 7-6, 6-3.
World No 10 Tsonga will play Thiemo de Bakker for a place in Saturday's semi-finals after the 21-year-old Dutchman upset seventh seed Juan Carlos Ferrero 7-6, 3-6, 7-6.
"I wasn't sliding well at the start, the clay was quite heavy," Tsonga said.
"Then I started to play a bit more how I play on hardcourts which enabled me to get back into the match in the second and third set."
Verdasco, losing finalist at last week's Monte Carlo Masters, will play Ernests Gulbis on Friday after the Latvian saw off Spanish qualifier Albert Ramos 6-1, 6-3.
"The court was very slow and I had to suffer a lot to win but I got a lot of support from the crowd at key moments," said Verdasco.
"I have to prepare for tomorrow's match now which is definitely going to be very tough."
Spanish eighth seed David Ferrer, runner-up to compatriot Rafael Nadal in 2008 and 2009, advanced when Simone Bolelli retired from their match with a wrist injury.
World No 17 Ferrer was leading 6-0, 3-0 when the Italian pulled out. He next plays Thomaz Bellucci after the Brazilian 13th seed beat Spain's Guillermo Garcia-Lopez 6-4, 6-4.
World No 3 Nadal, who has won the title for the past five years, skipped this week's event to give his body a rest after landing a record sixth consecutive Monte Carlo crown on Sunday.