World No 2 Alexander Zverev was knocked out of the Madrid Open in the round of 16 by Argentina's Francisco Cerundolo on Tuesday.
Cerundolo, ranked 21, beat the German - a two-time former winner in Madrid - 7-5, 6-3 to repeat his feat from last year.
The Argentinian will face Jakub Mensik in the quarter-finals after the Czech's straightforward 6-3, 6-2 victory over Kazakhstan's Alexander Bublik.
Matched game for game in the first set, Zverev offered up two set points to Cerundolo, who took the opening set at the second time of asking.
An over-hitting Zverev was broken immediately in the second set, allowing the 20th seed an advantage he built on to lead 4-1.
Zverev flung his racket to the ground in frustration, but Cerundolo kept his calm and served out for the match.