London - Andy Murray's reign as Queen's Club champion ended in stunning fashion on Thursday as Czech veteran Radek Stepanek clinched a shock 7-6 (12/10), 6-2 win over the world number five.
Murray's tame third round exit at the hands of the unheralded world number 42 is a major blow to his grass-court preparations less than two weeks before the start of Wimbledon, where he will defend the title he won so memorably last year.
It was also the 27-year-old's first loss since his surprise decision to hire Frenchwoman Amelie Mauresmo as his new coach last Sunday.
Since losing to Roger Federer in the 2012 Wimbledon final, Murray had been unstoppable on grass, but his 19-match winning run, which brought him Olympic gold, a first Wimbledon crown and a third Queen's title, came to a shattering halt in the west London sunshine.
Murray conceded he had no excuses after failing to take any of the eight set points he earned in the first set.
"I have only got myself to blame that I lost the first set. I don't know how many set points I had, but quite a lot of them were on my serve," he said.
"On this surface especially you shouldn't really be losing sets like that. That's what's disappointing about the match.
"Then unfortunately I got broke in the first game of the second set and I couldn't quite get it back."
Murray had revealed earlier on Thursday how his attempt to hire Mauresmo began with a nervous overnight wait to see if she would respond to his initial contact in a text message.
But on the evidence of this underwhelming display, their partnership, which has been the talk of the sport for the last week, might not last much longer than an initial trial period during the grass-court campaign.
In fairness to Mauresmo, Murray's malaise has lasted since he beat Novak Djokovic to end Britain's 77-year wait for a male winner of the Wimbledon singles title.
Since then, hampered by back surgery and his split with previous coach Ivan Lendl, Murray has failed to reach a single ATP Tour or Grand Slam final.
The British number one had hoped getting back on grass following his run to the French Open semi-finals would signal a further up-turn in his fortunes.
But this defeat suggests there is much to work on with Mauresmo if he is to repeat last year's Wimbledon heroics.
"I played well on the grass over the last few years, so I would have hoped to have done a bit better," Murray added.
"But like I said, it's more about how I get myself ready for Wimbledon now and how I use the next 10 days of preparation on the grass. Hopefully I can do a good job of that."
Stepanek's reward for just his second career win over Murray is a quarter-final clash with South African seventh seed Kevin Anderson, who defeated Sergiy Stakhovsky 6-3, 3-6, 7-6 (7/4).
"I am sorry to beat Andy in front of his home crowd," the 35-year-old said with a grin.
Former Wimbledon runner-up Tomas Berdych has never won the Queen's title, but the big serving Czech has the perfect game for grass and he booked his quarter-final berth with a 7-6 (7/2), 6-4 victory over France's Adrian Mannarino.
Berdych, the world number six, next plays Spanish 10th seed Feliciano Lopez, a 7-6 (7/3), 6-7 (4/7), 7-6 (7/3) winner over Kenny De Schepper.
Top seed Stan Wawrinka, the reigning Australian Open champion, routed former Queen's winner Sam Querrey 6-2, 6-2 in only 50 minutes.
Wawrinka's last eight opponent will be out-spoken Australian Marinko Matosevic, who shocked French fifth seed Jo-Wilfried Tsonga 6-2, 6-4 three days after his criticism of Murray's decision to hire Mauresmo.
Bulgarian fourth seed Grigor Dimitrov defeated Edouard Roger-Vasselin 7-6 (7/3), 6-4 and will face Ukraine's Alexandr Dolgopolov, who advanced when Jarkko Nieminen retired in the second set.
Results from the fourth day of the ATP Queens tournament on Thursday (x denotes seeding):
Stanislas Wawrinka (SUI x1) bt Sam Querrey (USA) 6-2, 6-2
Marinko Matosevic (AUS) bt Jo-Wilfried Tsonga (FRA x5) 6-2, 6-4
Grigor Dimitrov (BUL x4) bt Edouard Roger-Vasselin (FRA) 7-6 (7/3), 6-4
Oleksandr Dolgopolov Jr. (UKR x8) bt Jarkko Nieminen (FIN) 6-4, 4-2 retired
Kevin Anderson (RSA x7) bt Sergiy Stakhovsky (UKR) 6-3, 3-6, 7-6 (7/4)
Radek Stepanek (CZE x15) bt Andy Murray (GBR x3) 7-6 (12/10), 6-2
Tomas Berdych (CZE) bt Adrian Mannarino (FRA) 7-6 (7/2), 6-4
Feliciano Lopez (ESP x10) bt Kenny De Schepper (FRA) 7-6 (7/3), 6-7 (4/7), 7-6 (7/3)