Philipp Kohlschreiber won an all-German affair to send Rafa Nadal's conqueror Dustin Brown crashing out in Halle.
Kohlschreiber triumphed in an epic final set tie-break, eventually winning 6-4 5-7 7-6 (18/16) as he remains on course to repeat his 2011 tournament victory.
A solitary break was enough for Kohlschreiber to secure the first set before a topsy-turvy second saw a total of five breaks.
It was Brown who earned the decisive one to level the match and, after trading breaks in the decider, another breaker was required to separate the two.
A thriller ensued before the German no. 2 was finally able to put an end to proceedings and end the wilcard's run at the quarter-final stage.
Roger Federer made it through to the semi-finals without having to play a shot, courtesy of a walkover against Taiwan's Lu Yen-Hsun who was forced to withdraw through injury.
The Swiss has won the title in Halle on six previous occasions and is now just two matches away from adding a seventh.
Colombia's Alejandro Falla is also into the semi-finals after beating local favourite Peter Gojowczyk.
The 30-year-old left-hander won the match in straight sets but needed a tie-break at the end of each set to get the better of Gojowczyk.
The pair exchanged breaks in the opening set with the German looking the more likely to force another decisive break. As it was neither man found a breakthrough and it was Falla who prevailed in the breaker to take the set 7-6 (6/4).
The second set followed a similar pattern and again there was a break of serve apiece. However, Falla, buoyed by taking the first set, now appeared more likely to break again and it was no suprise to see him in control throughout the tie-break and wrap up a 7-6 (7/4) 7-6 (7/2) win.