Williamson made his professional debut in 2000 at the age of 32. He won his first eighteen fights out of 19, with 16 of them by knockout (KO) inside the first five rounds before facing another undefeated hard-hitting heavyweight Joe Mesi. In the opening minute, Mesi hit Williamson with a right-left combination, unleashing a barrage of punches which ultimately put Williamson down. Davarryl was not able to get up at the count of ten, declaring Mesi the winner by first-round KO.