Mahut knocked off El Aynaoui, 7-6 (7-4), 4-6, 7-6 (7-2), for his first win in four matches on the ATP Tour this season. The 21-year-old Frenchman has won three titles on the Challenger and Futures levels this year.
El Aynaoui had reached at least the quarterfinals in his previous two tournaments. He was a semifinalist at Long Island and was among the final eight at the U.S. Open.
David Ferrer of Spain beat Karol Beck of Slovakia, 6-1, 6-2, and Germany's Tomas Behrend beat Argentina's Mariano Puerta, 7-5, 6-4.