Former Aegon Championships winner Rafael Nadal crashed out in the first round at Queen's Club on Tuesday as he was beaten 6-3 6-7 (6-8) 6-4 by Alexandr Dolgopolov.
Nadal won in Stuttgart on Sunday to claim a first grass-court title since his 2011 Wimbledon success, but failed to build on that triumph on his return to Queen's as his build-up to the third slam of the year was hampered by a determined Dolgopolov.
The Ukrainian won the pair's last meeting in 2014 and repeated the feat with a resolute display, punctuated with some masterful passing shots, against the fifth seed.
Dolgopolov hurried into a three-game lead, having broken in the second with a whipped forehand on the run after fighting back from 40-15 down.
In front of watching Chelsea manager Jose Mourinho, Nadal saved three break points to get on the board in the fourth.
However, Dolgopolov stood firm as the Spaniard found his feet - a slick serve-volley combination putting the underdog within a game of the first set.
While Nadal made his opponent wait for an early advantage, his return from another powerful Dolgopolov serve went long to set the latter on course for an upset.
Nadal started the second set by salvaging a deep backhand that seemed a lost cause, and claimed his first three service games without dropping a point.
Dolgopolov was also able to hold firm - most impressively with a stunning forehand and ace at deuce in the eighth game - before Nadal saved a match point in the tie-break.
A crafty drop shot helped Nadal back into the match before a marginally wayward pass gave the 14-time grand slam winner an early break in the third.
However, aggressive play saw Dolgopolov break back at 4-4 with a fierce backhand volley and he saved three break-points in the next game before sealing victory by taking the Nadal serve again with a full-blooded forehand pass.
A second-round meeting with another Spaniard, Guillermo Garcia-Lopez, now awaits the world number 79.