American Mardy Fish has retired because of heat stroke during the third set of the Winston-Salem Open with Jarkko Nieminen leading 7-5, 6-7 (3), 3-2 on Tuesday.
Fish says in a statement he developed "heat stroke" and the "very hot and humid" weather made it difficult to continue the match.
Slovakia's Martin Klizan was upset 6-4, 6-1 by Spain's Roberto Bautista Agut in the second round. Eighth-seeded Juan Monaco of Argentina defeated France's Nicolas Mahut 6-7 (4), 6-3, 6-4 in the final hard-court tune-up before the U.S. Open.
Eleven seeded players had second-round matches Tuesday. Top seed Tomas Berdych and two-time defending champion John Isner withdrew Monday with injuries, and two other seeded players were upset that night.