Though he played in his second All-Star Game in 1990, Mullen's production fell by 41 points, to 69, and he failed to score at least 40 goals for the first time in six seasons. Concerned about his age, the Flames chose to trade the 33-year-old Mullen following the season. He was sent to the Pittsburgh Penguins in a draft day trade on June 16, 1990, in exchange for Pittsburgh's second round selection.