Borna Coric came from set down to surprise second seed Albert Ramos-Vinolas and reach the semi-finals of the Grand Prix Hassan II.
Ramos-Vinolas needed just the solitary break to win the first set but, after forcing a decider, Coric broke to love at 5-4 to seal a 4-6 6-4 6-4 triumph.
Another seed to suffer defeat was Paolo Lorenzi. The Italian fifth seed lost 3-6 6-3 7-6 (7-5) to Jiri Vesely, who now faces a semi-final with Coric.
"I didn't get off to a good start. Paolo is a great clay-court player and I was expecting a tough match," said Vesely.
"I always feel great in Morocco and I like to start the clay-court season here. The semi-final will be another tough match. Coric won a close match against Ramos-Vinolas, so I hope that I can play well again."
Philipp Kohlshcreiber fought from behind to see off fellow German Jan-Lennard Struff, the third seed winning 3-6 7-5 6-3.
There were no such problems for sixth seed Benoit Paire, though, as he beat Tommy Robredo - who knocked out top seed Grigor Dimitrov in the previous round - 6-2 6-4.