Haase came away a 4-6, 6-4, 6-3 winner over the third seeded Verdasco with three breaks over the final two sets. He didn't face a break point in taking the second set and finished off both of his own break opportunities in the third set to advance.
He'll go against No. 8-seeded Marcel Granollers in the semifinals Friday. Granollers was a 6-3, 6-1 victor against Leonardo Mayer. He saved the only two break chances for Mayer in the match while winning nearly three-quarters of the points on serve.
Also Thursday, second-seeded Juan Monaco defeated Daniel Gimeno-Traver 6-2, 3-6, 6-4 by cashing in the only break in the third set and Albert Montanes, seeded seventh, took out Dominic Thiem 6-4, 6-3, fighting off seven break points.
Haase and Granollers have split their two previous meetings with Haase taking a three-set decision from Granollers in a quarterfinal match last week in Switzerland. Montanes is 2-1 lifetime versus Monaco.