South African slugger Kevin Anderson posted a first-round victory and Spaniard Feliciano Lopez worked out a second-round triumph on Wednesday at the U.S. Men's Clay Court Championship.

The fifth-seeded 6-foot-8 Anderson, a titlist in Florida last month, handled Brazilian Joao Souza 6-3, 6-4 in 1 hour, 54 minutes at River Oaks Country Club.

America Ryan Harrison closed out Wednesday's first round by taking care of Russian Alex Bogomolov, Jr. with a 4-6, 6-3, 6-4 decision that took two hours, 18 minutes.

Lopez needed nearly two hours to subdue his opponent, Italian Paolo Lorenzi. After taking a grueling first set by a 6-4 count, Lopez was taken to a tiebreaker in the second but eventually pulled out a 7-6 (7-4) victory.

In the earlier second-round pairing, six-seed Argentine Carlos Berlocq breezed by Germany's Bjorn Phau 6-1, 6-0.

An opening-round upset came when American journeyman Bobby Reynolds upended eighth-seeded Croat Ivo Karlovic, 7-6 (7-5), 2-6, 6-3. The 2007 Houston champion Karlovic lost despite uncorking 19 aces on Day 3.

Top seeds Mardy Fish and John Isner will see their first action of the week on Thursday, when the 2006 Houston champ Fish faces Houston resident and fellow American Michael Russell and the 6-foot-9 Isner takes on Argentine Horacio Zeballos.

The winner of this $442,500 event will take home $79,880.