Nicolas Almagro was dumped out of the German Tennis Championships by Paul-Henri Mathieu, but top seed Philipp Kohlschreiber fought back from a set down to beat Nicolas Kicker and seal a quarter-final spot.
Sixth seed Almagro was ousted by Denis Istomin in the second round at Wimbledon and suffered another setback on Wednesday, with the unseeded Mathieu beating the Spaniard 4-6 7-6 (7-4) 7-5 in Hamburg.
Mathieu is ranked 22 places below Almagro, but the Frenchman took his record against the world number 44 to 4-1 in his favour despite serving 11 double faults at the Rothenbaum Tennis Center.
Almagro blasted down 16 aces, but could only convert three of 14 break points and also failed to hold on three occasions to miss out on a place in the last eight.
Top seed Kohlschreiber moved a step closer to a tournament victory on home soil, recovering from losing the opening set to see off unseeded Argentine Kicker 4-6 6-1 6-2.
Kohlschreiber will face Renzo Olivo at the quarter-final stage after he came out on top in an all-Argentina round-of-16 match against Maximo Gonzalez, winning 6-3 6-4.
Third seed Pablo Cuevas, eyeing a third ATP World Tour title of the season, beat qualifier Thiago Monteiro 6-3 6-2 in the other match to be played on Wednesday.