Haas, playing in the city of his birth, eliminated Simon 4-6, 6-3, 6-4. He had five breaks over the last two sets in the win. He needed three breaks just to survive the second set and then had a pair in taking the third set.
No. 4-seeded Marin Cilic capped the day's schedule with a 6-3, 6-2 victory over Federico Delbonis. Cilic saw just one break point in the match. He was good on more than half of his first serves and won the point on 81 percent of those situations.
Seven-seeded Florian Mayer sailed past Robin Haase 6-2, 6-1 in 56 minutes. Mayer lost six points over seven games serving.
Wednesday's other match saw Albert Ramos edge Lukas Rosol 7-6 (10-8), 4-6, 6-3. That match took more than 2 1/2 hours.
Ramos will go against Cilic and Mayer is to play Haas in Friday's quarterfinals.