Rain has hampered play over the first three days.
Ljubicic beat Czech Jan Hajek 4-6, 6-0, 6-3, and Querrey beat Austrian Oliver Marach 3-6, 6-4, 6-4 in a match that had been suspended because of rain Monday.
Rain completely washed out play Sunday and, combined with darkness, forced seven first-round matches to be either suspended or postponed Tuesday.
Four other seeds had their first-round matches postponed Tuesday. No. 2 Argentine Juan Monaco, No. 4 American Mardy Fish, No. 7 Croat Mario Ancic and No. 8 Dutchman Robin Haase will have to wait until Wednesday to open their play. Monaco is the reigning champion, beating Frenchman Gael Monfils in last year's Portschach finale.