Top-seeded Haas of Germany waltzed past American qualifier Wayne Odesnik in 55 minutes by a score of 6-2, 6-1.
Isner, the No. 2 seed, had a rougher time with fellow American Michael Russell but prevailed 4-6, 7-6 (7-3), 6-4. Russell won 17-of-19 first serves in the first set, but Isner won 15-of-16 first serves in the final set and also served five aces.
Other winners Tuesday included third-seeded Kei Nishikori of Japan, who topped qualifier Gastao Elias 6-1, 5-7, 6-2. Fourth-seeded Kevin Anderson of South African downed American Tim Smyczek 4-6, 6-1, 6-3.
Fifth-seeded Rhyne Williams advanced when Alejandro Falla retired, and eight-seeded Australian veteran knocked off American Bradley Klahn 6-3, 6-1.