Spaniard Jaume Munar stunned top-seeded German Alexander Zverev 7-6 (1), 2-6, 6-3 on Thursday in the second round of the Grand Prix Hassan II at Marrakesh, Morocco.
Munar, ranked 60th in the world, needed 2 hours and 27 minutes to take down the world's third-ranked player. He won four points on Zverev's serve in the first-set tiebreaker, then bounced back from a second-set loss to break Zverev three consecutive times to close out the match.
The other seeded players in action also fell, as Spaniard Pablo Andujar took down seventh-seeded German Philipp Kohlschreiber 7-6 (6), 6-4, and Frenchman Benoit Paire dumped eighth-seeded countryman Pierre-Hugues Herbert 6-4, 6-2. Paire will face Munar in the quarterfinals.
In the day's other match, Jiri Vesely of the Czech Republic dispatched Argentina's Juan Ignacio Londero 6-3, 6-4.
U.S. Men's Clay Court Championship
Top-seeded Steve Johnson was upset in front of a home crowd, falling 6-3, 6-3 to Colombia's Daniel Elahi Galan in the second round at Houston.
Galan, ranked No. 241 in the world, downed Johnson, ranked 39th, in just 75 minutes, converting all three of his break points and facing none on his own serve.
Third-seeded Cameron Norrie of Great Britain was also ousted, losing 6-3, 6-4 to Janko Tipsarevic of Serbia. Eighth-seeded American Sam Querrey had better luck, downing Spaniard Guillermo Garcia-Lopez 6-4, 6-3.
In the evening's final match, Colombia's Santiago Giraldo opposed seventh-seeded Australian Jordan Thompson.