Juan Martin del Potro, the 2009 U.S. Open champion, had issues with the heat but still advanced along with No. 19 Tomas Berdych, No. 21 Albert Ramos and No. 5 Dominic Thiem, who rallied to beat 190th-ranked American qualifier Denis Kudla 6-7 (6), 3-6, 6-3, 6-2, 6-3. (Photo | AP)