Wawrinka lost just three games as he brushed the Spaniard aside 6-1 6-2 to earn a spot in the last four against Tommy Robredo.
Veteran Robredo beat fourth seed Benoit Paire 7-6(4) 2-6 6-0, making Paire the only one of the top four seeds not to make the semis.
Casablanca Open men's quarter-final results:
3-Martin Klizan (Slovakia) beat 7-Robin Haase (Netherlands) 7-5 6-1
2-Kevin Anderson (South Africa) beat 8-Grega Zemlja (Slovenia) 6-4 6-4
1-Stanislas Wawrinka (Switzerland) beat Guillermo Garcia-Lopez (Spain) 6-1 6-2
Tommy Robredo (Spain) beat 4-Benoit Paire (France) 7-6(4) 2-6 6-0
U.S. Clay Court Championship men's quarter-final results:
Rhyne Williams (U.S.) beat Ruben Ramirez Hidalgo (Spain) 7-6(1) 1-6 6-4