Top seed Grigor Dimitrov suffered a stunning defeat to Tommy Robredo in the second round of the Grand Prix Hassan II in Marrakech on Thursday.
Dimitrov went into the match with a 17-4 record in 2017, although his form has tailed off in recent weeks - suffering early exits in Indian Wells and Miami - and his slump continued with a 6-4 1-6 6-1 loss to Robredo.
The Bulgarian looked set to recover after levelling the match in comfortable fashion but Robredo won the first three games in the decider and went on to break Dimitrov again as he set up a quarter-final clash with Benoit Paire.
Paire eased to a 6-2 6-2 triumph against Radu Albot, while Philipp Kohlschreiber saw off Jeremy Chardy 6-0 2-6 6-3. German compatriot Jan-Lennard Struff, a winner over Amine Ahouda, is next up for Kohlschreiber.
Jiri Vesely sprung a surprise by overcoming fourth seed Mischa Zverev 6-4 6-4, and he will meet fifth seed Paolo Lorenzi after the Italian laboured to beat countryman Gianluigi Quinzi 7-6 (7-5) 2-6 6-4.