The giant American was the third seed for the tournament but Russia's Evgeny Donskoy fought back after losing the first set on a tie-break to win 6-7 (3/7) 6-3 6-4.
It was not a good day for the seeds, with Marcos Baghdatis, Daniel Gimeno-Traver and Victor Hanescu also going out.
For sixth seed Bahgdatis, beaten 6-2 6-4 by Carlos Berlocq, it was a ninth successive first-round defeat.
The Cypriot said on www.atpworldtour.com: "I'm going through tough times.
"Confidence-wise, head-wise, everything's spinning when I'm on the court. I'm thinking very negatively on the court. It was a terrible match.
"Today was a terrible day. In practice I'm playing so good and I want to do everything perfect on the court. I am putting too much pressure on myself.
"I need to fight and win some matches and just focus on that, not trying to play perfectly all the time."
Seventh seed Hanescu lost to Guillermo Garcia-Lopez while Gimeno-Traver was beaten by Andrey Kuznetsov.
In the women's event, second seed Dominika Cilbulkova was given a real battle by Lourdes Dominguez Lino before coming through 6-1 6-7 (5/7) 7-6 (7/3).
Third seed Carla Suarez Navarro had no problems against Johanna Larsson but fifth seed Mona Barthel and eighth seed Kristina Mladenovic both lost.
Romania's Simona Halep, the champion in Nurnberg last week, continued her good form with a 6-1 2-6 6-3 victory over Annika Beck.