The 6-foot-10 Karlovic dropped the first set 4-6 against Marcos Baghdatis, but was leading 2-1 in the second when his opponent from Cyprus retired from the match due to a back injury. Karlovic will face former world No. 1 Carlos Moya in the round of 16.
Simon was upset by wild card fellow Frenchman Nicolas Mahut, 6-4, 3-6, 6-1. In another Tuesday upset, Argentine Eduardo Schwank defeated third-seeded Spaniard Nicolas Almagro, 7-6 (7-5), 6-2.
Also, fourth-seeded Paul-Henri Mathieu beat fellow Frenchman Nicolas Devilder, 6-0, 6-2, and fifth-seeded Russian Dmitry Tursunov beat Frenchman Thierry Ascione, 6-7 (3-7), 6-2, 6-4.
Romanian Victor Hanescu beat Croat Ivan Ljubicic, 6-1, 7-6 (7-4), and Frenchman Marc Gicquel beat Spaniard Marcel Granollers, 6-3, 6-2.
Ljubicic won this event in 2005.
Swim Week Miami Beach 2014 [PHOTOS]