Andreev beat Belgian Olivier Rochus 6-3, 6-4, while Fish, who was last year's New Haven runner-up to fellow American James Blake, defeated American Wayne Odesnik 6-1, 4-6, 6-1. Karlovic dropped his first set to American John Isner, but rebounded to win 6-7 (4-7), 6-3, 6-4 victory.
German Mischa Zverev beat fifth-seeded Argentine Juan Monaco 6-3, 6-3 and sixth-seeded Marin Cilic of Croatia was leading last week's Washington runner-up Viktor Troicki, 2-1, when the Serbian retired.
Also, No. 7 Italian Andreas Seppi came back against countryman Potito Starace 4-6, 6-4, 6-4; No. 9 Frenchman Marc Gicquel beat Spaniard Albert Montanes 7-5, 6-3; and Fabio Fognini eliminated fellow Italian Simone Bolelli 6-2, 5-7, 6-4.