Becoming a free agent following the 1990–91 season, Shanahan was signed by the St. Louis Blues on July 25, 1991. According to the collective bargaining agreement, he was a restricted free-agent, and therefore, the Devils were due compensation. Ordinarily, this compensation would be in the form of draft picks, but the Blues already owed four first-round draft picks to the Washington Capitals for signing defenceman Scott Stevens the previous year. The Blues made an offer for compensation that consisted of Curtis Joseph, Rod Brind'Amour and two draft picks even further down the road. However, the Devils were only interested in Scott Stevens. An arbitrator eventually decided that Stevens was to be the compensation, so Shanahan joined the Blues in exchange for Scott Stevens.