Halle - Milos Raonic of Canada defeated Ze Zhang of China 6-1, 6-1 on Wednesday to set up a possible quarter-final with five-time Gerry Weber Open champion Roger Federer.
Raonic made short work of the 217th-ranked qualifier in the second round of the grass-court tournament, breaking Zhang in the fourth game and taking just 20 minutes to win the first set, which he ended with his fifth ace.
The 21st-ranked Raonic had nine aces in the 52-minute win.
He will next face 16-time Grand Slam winner Federer or Florian Mayer of Germany, who meet on Thursday.
Third seeded Tomas Berdych of the Czech Republic also reached the quarter-finals after beating Viktor Troicki of Serbia 6-3, 6-2.
The No 7-ranked Berdych was not broken during an hour-long match against the Troicki, who is ranked No 33.
Mikhail Youzhny of Russia eliminated the fourth-seeded Alexandr Dolgopolov of Ukraine 6-4, 3-6, 6-3.
Youzhny will next play the winner of a match between Radek Stepanek of the Czech Republic and Cedric-Marcel Stebe of Germany, who are playing later on Wednesday.
Also in action is seven-time French Open champion Rafael Nadal who will team up with compatriot Marcel Granollers for a doubles match against Troicki and Michal Mertinak of Slovakia.
Nadal will open in singles on Thursday against Lukas Lacko of Slovakia.