Brock made his professional debut on February 11, 2001, knocking out Zibielee Kimbrough in the third round. He built up a 23–0 record with 19 knockouts before stepping up in competition, facing Clifford Etienne. Etienne, once highly regarded prospect, was looking for a way to regain his stock after being knocked out by Mike Tyson and Fres Oquendo. Coming into the bout, Etienne was 5–0–1 in his last six fights. The bout took place in Reliant Center in Houston, Texas, and was aired on ESPN2. Brock knocked down Etienne three times, once in round two and twice in round three, with the referee stopping the fight after the third knockdown, declaring Brock the winner by third-round TKO.