 Signing an amateur try-out contract the following day with Colorado's American Hockey League (AHL) affiliate, the Hershey Bears, Liles made his professional debut against the Grand Rapids Griffins on March 30 and played in ten games to end the 2002–03 season.In the 2003–04 season, Liles made the Avalanche roster out of college and scored his first NHL goal and point, a game-winner, against the Minnesota Wild on October 16, 2003.He led all rookie defensemen with ten goals and 34 points in 79 games to be named to the NHL All-Rookie Team while also becoming highest point-scoring rookie defenseman in Avalanche history, and second in franchise history since Bruce Bell's 37 with the Quebec Nordiques in 1984–85.