Third seed Nick Kyrgios is out of the European Open after a surprise 6-7, 6-3, 6-3 defeat to Ruben Bemelmans.
The controversial Australian looked to be in the ascendancy after shading a tight opening set via a tie-break but fell away thereafter as Belgium's Bemelmans surged to a clash with Joao Sousa.
Sousa secured his place in the quarterfinals in Antwerp with a 5-7, 6-4, 6-4 victory over Sergiy Stakhovsky.
The Portuguese was edged out by his Ukrainian opponent in the opening set but recovered impressively to book a place in the last eight.
Also waiting for confirmation of his quarterfinal opponent is France's Julien Benneteau, who enjoyed a serene 6-1, 6-1 success over Henri Laaksonen.
Meeting No. 5 seed David Ferrer in the last 16 will be Steve Darcis after Germany's Cedrik-Marcel Stebe retired with the Belgian leading 4-6, 6-4, 1-0.