Darcis, ranked 72nd in the world, will next face French fifth seed Julien Benneteau, who ousted Luxembourg's Gilles Muller 6-2, 6-4 in another second-round match on Thursday, at the indoor hardcourt event.
In his 10th professional season, 27-year-old Darcis is seeking his third ATP title after a 2007 triumph in Amersfoort and a 2008 victory in Memphis.
French top seed Gael Monfils withdrew with a right knee injury and was replaced by US lucky loser Blake Strode, who was eliminated by Bulgarian Dimitar Kutrovsky 7-5, 6-3.
South African sixth seed Kevin Anderson dispatched Australian Matthew Ebden 6-1, 6-2 to book a quarter-final date against defending champion and third seed Milos Raonic of Canada.
What the stars mean:
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