John Isner was one of four seeded men's players to lose in the first round at the rain-interrupted Topshelf Open.
The third-seeded American lost 6-7 (3), 6-3, 6-4 to Evgeny Donskoy on Monday. No. 6 Marcos Baghdatis of Cyprus, No. 7 Victor Hanescu of Romania and No. 8 Daniel Gimeno-Traver of Spain were also upset.
Donskoy earned breaks against the big-serving Isner early in the second set and again in the final set to advance at the Wimbledon warm-up.
Carlos Berlocq beat Baghdatis 6-2, 6-4. Hanescu lost 6-4, 6-3 to Guillermo Garcia-Lopez, and Andrey Kuznetsov beat Gimeno-Traver 7-6 (4), 6-3.
Defending champion David Ferrer, the French Open runner-up, opens play Tuesday against Xavier Malisse.
In the women's event, second-seeded Dominika Cibulkova beat Lourdes Dominguez Lino 6-1, 6-7 (5), 7-6.
Third-seeded Carla Suarez Navarro advanced with a 6-3, 6-2 win over Johanna Larsson, and Lauren Davis of the United States defeated Andrea Hlavackova 6-3, 6-4.
