Eighth-seeded Juan Monaco of Argentina defeated France's Nicolas Mahut 6-7 (4), 6-3, 6-4 in the hardcourt tuneup for next week's US Open.
Mardy Fish retired in the third set of his match with No. 11-seeded Jarkko Nieminen, who was leading 7-5, 6-7 (3), 3-2 when his American rival quit because of heat stroke.
Fish said in a statement he developed "heat stroke" and the "very hot and humid" weather made it difficult to continue the match.
In other second-round matches, fifth-seeded Benoit Paire of France beat American James Blake 7-6 (9), 2-6, 6-3; seventh-seeded Fernando Verdasco of Germany beat American Tim Symczek 3-6, 6-3, 6-3; ninth-seeded Jurgen Melzer of Austria beat qualifier Thiemo de Bakker 7-5, 6-7 (4), 4-2; and 13th-seeded Dmitry Tursunov of Russia defeated qualifier David Goffin of Germany 4-6, 7-5, 6-1.