Jiri Vesely set up a quarter-final meeting with number one seed Guillermo Garcia-Lopez after a hard-fought victory over Nikola Mektic at the Grand Prix Hassan II on Thursday.
Eighth seed Vesely had to battle for more than three hours to overcome the tricky qualifier.
The Croatian claimed the first set through a tie-break, but Vesely fought back to complete a 6-7 (4-7) 6-3 7-6 (7-5) win, hitting 15 aces in the process.
Garcia-Lopez - winner of the competition in 2014 - was also forced to fight back from an opening-set loss to book his place in the last eight.
The top seed received a bye in the first round and started sluggishly against fellow Spaniard Nicolas Almagro.
However, Garcia-Lopez responded emphatically to secure a 1-6 6-3 6-4 victory, ending a run of three straight defeats against his compatriot.
A dominant service game saw Pablo Carreno Busta beyond Denis Istomin 6-3 7-6 (7-5), and he will meet Federico Delbonis in the quarter-final after the Argentinian routinely dispatched Thiemo De Bakker 6-4 6-4.