Fifth seed Lukas Rosol was a first- round loser Sunday at the inaugural Power Horse Cup, a final French Open tune-up.
Rosol, the only seeded player to see action on the red clay at Rochusclub, lost 6-4, 6-3 to German Daniel Brands.
Brands will face another Czech in the second round after Jan Hajek saved all six breaks points in a 6-2, 6-2 win over Russian Evgeny Donskoy.
Croat Ivan Dodig also beat Slovenia's Blaz Kavcic 7-5, 6-4 on Day 1.
Dusseldorf used to play host to the ATP World Team tournament.