London - Rafael Nadal suffered a shock first-round exit from the Wimbledon warm-up event at Queen's Club as the Spanish star was beaten 6-3, 6-7 (6/8), 6-4 by unheralded Ukrainian Alexandr Dolgopolov on Tuesday.
Nadal's dismal defeat against the world number 79 is the latest in a growing list of lacklustre performances in a troubled 2015 campaign for the former world number one.
The 14-time Grand Slam winner was beaten at the French Open for only the second time in his glittering career when Novak Djokovic won their quarter-final clash in Paris.
As a result, Nadal's ranking has plunged to 10th - his lowest position for a decade - and to add insult to injury he will now head to Wimbledon, which gets underway later this month, with renewed questions about a decline that hit another low with this setback in west London.
Nadal tried to downplay the significance of the result, saying: "It's a loss. I didn't play bad at all and fought until the end. Games on grass are like this.
"I played an uncomfortable player. Sometimes just a few things decide matches here and I wasn't lucky enough today. I probably didn't play aggressive enough when I had the break in the third set."
Dolgopolov added: "It's as good as I've played on grass. I like to frustrate opponents and make it uncomfortable for them."
Nadal, back at Queen's for the first time in four years, wasn't expected to have any problems with Dolgopolov after the confidence booster of winning the grass-court tournament in Stuttgart last week -- his first title on the surface since lifting the Wimbledon crown five years ago.
But Dolgopolov had won his last meeting with Nadal - at Indian Wells last year - and dominated from the baseline as he took the first set.
In a dramatic second set tie-break, Nadal saved a Dolgopolov match point with a nerveless serve and went on to level the match.
Nadal looked firmly in control after breaking in the third game of the final set, but he let the momentum, and a 4-2 lead, slip away when, after being given a warning for a time violation, he allowed Dolgopolov to break back.
There was more frustration for Nadal at 4-4 when he wasted three break points and that proved the decisive moment after Dolgopolov unloaded a searing winner on match-point in the next game to steal a sensational victory.
Three-time Queen's champion Andy Murray had no such problems as he saw off Taiwanese qualifier Lu Yen-Hsun 6-4, 7-5.
The 28-year-old top seed is coming off the best clay-court campaign of his career after taking titles in Madrid and Munich before pushing Djokovic to five sets in the French Open semi-finals.
He was never at his best against Lu, who enjoyed one of the best moments of his career when he defeated Murray at the 2008 Beijing Olympics.
But the former Wimbledon winner had enough guile to eventually subdue the 31-year-old world number 63 and set up a second-round clash with Spain's Fernando Verdasco.
"I felt like I moved pretty well. I didn't start serving so well. But I hit the ball well from the back of the court," Murray said.
"I've had good runs here. It's an extremely strong field this year so I'll have to play great tennis."
Meanwhile, French Open champion Stanislas Wawrinka returned to action after his Paris triumph with a 6-3, 6-4 dismissal of Australian rising star Nick Kyrgios.
The Swiss second seed swept through his first-clash in just 49 minutes to set up a second-round meeting with big-serving South African Kevin Anderson.
There was better news for another promising Australian as 19-year-old Thanasi Kokkinakis defeated Jeremy Chardy 6-7 (3/7), 6-2, 6-4 to earn a clash with French seventh seed Gilles Simon, a 6-7 (6/8), 7-5, 6-2 winner against Belgium's David Goffin.
Defending Queen's champion Grigor Dimitrov moved into the second round, where he faces Gilles Muller, after a 4-6, 6-3, 6-4 victory against 2010 winner Sam Querrey.