Delray Beach, FL (SportsNetwork.com) - American hopeful Jack Sock was a first- round loser Monday at the Delray Beach Open tennis event.

French left-hander Adrian Mannarino humbled the 21-year-old wild card Sock in 6-4, 6-2 fashion on the hardcourts at Delray Beach Tennis Center.

This week's top seeds in Florida are 2006 champion Tommy Haas and towering American John Isner.

Two-time champion Ernests Gulbis of Latvia defeated France's Edouard Roger- Vasselin in last year's final. Gulbis, however, is not defending his title this week.