Rain saw the second day of the US Men's Clay Court Championship in Houston postponed without a ball being hit.
Spanish seeds Feliciano Lopez and Fernando Verdasco were among those scheduled to play at River Oaks, but they will now return on Wednesday after the weather intervened in Texas.
Meanwhile it was a tough day for the seeds at the Grand Prix Hassan II in Morocco.
Number seven Diego Schwartzman and eighth seed Marcel Granollers both crashed out in straight sets.
Spaniard Granollers was beaten 6-4 6-4 by local wildcard Amine Ahouda, while Argentina's Schwartzman suffered a 6-3 6-2 last-32 defeat to Borna Coric.
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Ahouda was joined by compatriot Reda El Amrani in the last 16 after Federico Delbonis retired at 7-6 (7-3) 1-0 down in Marrakesh, while qualifier Gianluigi Quinzi beat Paul-Henri Mathieu 7-6 (10-8) 6-3.
