Halle - Second seed Dominic Thiem suffered a surprise second-round defeat by Robin Haase in Halle on Wednesday, but home favourite Alexander Zverev cruised into the quarter-finals.
Dutchman Haase got the better of Thiem 6-3, 7-6 (9/7), after the fourth-seeded Zverev had brushed aside his fellow German Philipp Kohlschreiber 6-3, 6-4.
Austrian Thiem was playing in his first tournament since reaching the French Open last four earlier this month, looking to get some match practice on grass before the start of Wimbledon on July 3.
But the world number 42 Haase grew into the match after saving two break points in the first game, and took the opening set thanks to a break in game eight.
Thiem, who beat Novak Djokovic at Roland Garros before being thrashed by Rafael Nadal, broke his opponent when he served for the match to force a second-set tie-break.
But Haase saved three set points in the breaker and wrapped up the win at the first time of asking to set up a last-eight tie with Richard Gasquet.
"It was not the best start I've had. The first set was pretty average," Thiem told the ATP Tour website.
"I played good in the second set and had a lot of chances, but he played those set points well and was playing well overall.
"I hope to get some matches next week (in Antalya) and then get ready for Wimbledon."
Earlier, Zverev, 20, had confidently dispatched of Kohlschreiber in just 65 minutes.
A break of serve in each set was enough for the Italian Open champion to reach his seventh quarter-final of the season, where he will take on seventh-seeded Spaniard Roberto Bautista Agut.
"I'm very satisfied because Philipp is someone who can play very well on grass. He mixes it up well with his slice and serve, so he's always a difficult opponent on this surface," said Zverev, the world number 12.
"I'm glad I could win in two sets and have the feeling I played well."
In the day's other matches, Gasquet followed up his surprise win over fellow Frenchman Gael Monfils by beating Bernard Tomic 6-3, 6-3, while Bautista Agut got the better of Dustin Brown 6-4, 1-6, 7-6 (8/6).
Roger Federer will continue his bid for a ninth Halle title on Thursday when he takes on Zverev's older brother Mischa.
Results from the ATP tournament in Halle on Wednesday (x denotes seeding):
Roberto Bautista Agut (ESP x7) bt Dustin Brown (GER) 6-4, 1-6, 7-6 (8/6)
Alexander Zverev (GER x4) bt Philipp Kohlschreiber (GER) 6-3, 6-4
Richard Gasquet (FRA) bt Bernard Tomic (AUS) 6-3, 6-3
Robin Haase (NED) bt Dominic Thiem (AUT x2) 6-3, 7-6 (9/7)