The Atlanta Flames selected Reinhart with their first round selection, 12th overall, at the 1979 NHL Entry Draft. Though he had been set to join Team Canada for the 1980 Winter Olympics, the Flames convinced Reinhart to sign with the team and begin his professional career instead. Joining the Flames for the 1979–80 NHL season, the 19-year-old Reinhart became the youngest player to appear for the team at that point in franchise history. He appeared in 79 games for Atlanta, finishing as the team's highest scoring defenceman. His total of 47 points was second to Ray Bourque for the overall lead amongst rookie defencemen.