Hamlett then started his professional career in 1992, splitting his time between indoor and outdoor soccer leagues--first for the Harrisburg Heat of the NPSL and the Fort Lauderdale Strikers of APSL. Then from 1994-95, he played indoor soccer for the Anaheim Splash of the CISL. In 1996, Hamlett was drafted by the Colorado Rapids in the second round, 12th overall in Major League Soccer's inaugural draft. His stellar play continued with Colorado, where he won the BIC Tough Defender of the Year award.
Hamlett continued his coaching duties with the Chicago Fire, becoming the top assistant coach in 2001. Upon dismissal of former head coach Dave Sarachan, Hamlett received interim head coaching duties on June 20, 2007, but resumed assistant coaching duties following the arrival of Juan Carlos Osorio. Orsorio has since resigned take on the head coach job at the New York Red Bulls, and Hamlett was hired as the head coach.