Tommy Haas and Florian Mayer have set up an all German quarter-final at the BMW Open in Munich.
Daniel Brands also advanced and, with Phillip Kohlschreiber winning on Wednesday, the home fans will have four players to cheer on in the last eight.
Third-seed Haas overcame Ernests Gulbis despite a second-set wobble. Haas claimed the first set but dropped the second on a tie-break before powering to a 6-4 6-7 (3/7) 6-1 win.
Mayer was also taken to three sets as he dropped the first against Marinko Matosevic but recovered to ease to a 2-6 6-4 6-2 win.
Brands was a surprise winner as he upset Gael Monfils.
The 25-year-old claimed the first set 6-3 but Monfils, who reached number seven in the world two years ago, fought back to claim the second.
He had no answer the third, however, as the world number 69 emerged a 6-3 3-6 6-0 victor.
In Thursday’s other game, top-seed Janko Tipsarevic was relatively untroubled as he beat Grega Zemlja 6-4 6-2.
