Alexander Zverev came through his Grand Prix Hassan II opener unscathed, but other seeds were not so fortunate on Tuesday.
Top seed Zverev was up against Denis Istomin and progressed with a minimum of fuss in the final match of the day, winning 6-4 6-4.
The German broke twice and held off Istomin's attempts to fight back, Zverev ultimately advancing without needing to exert himself too much.
Fabio Fognini did not have it so easy, though, and the second seed bowed out early as Jiri Vesely sprang a surprise to win 7-6 (7-2) 6-4.
Vesely said: "Fabio is unpredictable. He can play at top-five level and I got a bit nervous when he started playing unbelievably well at 5-1 in the second set."
It was a theme that continued throughout the draw on Tuesday, with fifth seed Laslo Djere stunned 6-3 6-3 by qualifier Lorenzo Sonego.
Sixth seed Fernando Verdasco is also out, going down to compatriot Adrian Menendez Maceiras in three sets, but Philipp Kohlschreiber and Pierre-Hugues Herbert joined Zverev in the next round.
There were also wins for Benoit Paire, Juan Ignacio Londero, Jaume Munar, Robin Haase and Pablo Andujar.
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