Melzer edged past Lukasz Kubot 7-6 (7-3), 7-6 (7-2) despite losing his serve three times. Kubot had 13 aces but also nine double faults. Melzer won two-thirds of the 33 points off Kubot's second serve.
He'll meet seventh-seeded Philipp Kohlschreiber in the quarterfinals. Kohlschreiber won the first four games of the third set in a 6-4, 3-6, 6-1 victory over Tobias Kamke. Kamke lost his serve four times in the match with the first one costing him the first set and the other three putting him in a 1-5 third-set hole.
Second-seeded Marin Cilic also booked a quarterfinals spot, topping Jan Hajek 7-6 (7-4), 6-2 behind an 11-ace attack. Cilic dropped his serve just once, saving 9-of-10 break points from Hajek.
Bjorn Phau claimed the tournament's final first-round win, beating Florian Mayer 6-2, 6-4 and saving the only break point he faced.