Germany's Tommy Haas beat world number nine Jo-Wilfried Tsonga 6-3, 7-6 on Wednesday to book his spot in the grasscourt Halle tournament quarter-finals.
Haas, who missed much of last year due to a shoulder injury, joined fellow Germans Mischa Zverev, Philipp Kohlschreiber and wildcard Benjamin Becker in the last eight where they could be joined by three more countrymen on Thursday.
Haas, ranked 41st in the world, broke the French fourth seed to go 3-0 up in the first set. Rushing to the net at every opportunity the 31-year-old wrapped it up after only 26 minutes.
Both big-serving players held serve in the second to take it to a tie-break with Haas clinching victory on his first match point after 79 minutes.
"It is difficult to remember another match on grass in my career that I played at such a consistently high level," said Haas, who lost a tight five-setter with Roger Federer at the French Open.
"Today I played as good as I can play and that is the only reason I won.
"Roland Garros was a boost and now this. After so many injuries it is important to feel you still have it," added Haas, who now faces Zverev.
Zverev saved two match points to edge past Czech Tomas Berdych 3-6, 6-2, 7-6.
Berdych, a winner in Halle two years ago, grabbed two breaks to win the first set before the gutsy 21-year-old hit back in the second.
The pair traded breaks in the third set before left-hander Zverev went 5-4 up. Berdych, who littered the court with 47 unforced errors, forced a tie-break, saving three match points at 6-3 before squandering two match points of his own.
Kohlschreiber joined him in the last eight with a 6-4, 7-6 win against Dmitry Tursunov. Kohlschreiber carved out a solitary break to grab the first set before the Russian briefly upped his game to go 4-1 up in the second.
Kohlschreiber levelled to take it to a tie-break and then clawed his way back from 5-0 down to win it 8-6 courtesy of a series of thundering backhands down the line.
Becker emerged victorious against countryman Rainer Schuettler 6-4, 2-6, 6-4.
World number four Novak Djokovic is in action against Frenchman Florent Serra on Thursday.
