Ivo Karlovic ousted sixth seeded German Benjamin Becker 7-5 7-6 in the first round of the U.S. Clay Court Championships on Monday.
Third seed Rainer Schuettler of Germany was the first casualty at the ATP Chennai Open.
The duo beat James Blake and Jeff Morrison of the U.S. in the first round of the ATP International tennis championship in Florida.
The top seed will face Kenneth Carlsen in the semi-finals after the unseeded Dane beat American Jan-Michael Gambill at the Kroger St Jude ATP event.