O'Connell was born in Chicago, Illinois, but spent much of his youth in Cleveland, Ohio, and Cohasset, Massachusetts. He played hockey for Archbishop Williams High School as a freshman and sophomore. As a junior, he skated for the Braintree Hawks of the New England Amateur Hockey League where, as a 16-year-old, he was often pitted against players 10 years his senior.

The talented blueliner opted to play junior hockey in Canada rather than attend a U.S. college. He became a playmaking standout for two years with the OHA's Kingston Canadians. After scoring 73 points in 50 games for Kingston in 1974-75, he was taken 43rd overall by the Chicago Blackhawks at the amateur draft. That year he was also voted on to the OHA first all-star team. He spent his first three pro seasons with the Dallas Black Hawks of the CHL and registered 135 assists during that period. After scoring 68 points in 63 games in 1976-77, he was named the top defenceman in the CHL and placed on the league's first all-star team.

O'Connell became a fan favorite in the Windy city by scoring 26 points in 48 games as a rookie in 1978-79. He played a solid role on the Hawks' blueline for another year-and-a-half until he was sacrificed to the Boston Bruins for power-forward Al Secord. O'Connell adjusted well to his new surroundings and was a member of Team USA at the 1981 Canada Cup.

The crafty playmaker was a constant in the Bruins' lineup for the equivalent of over five seasons and was often teamed with steady Mike Milbury. In 1982-83 he recorded a plus/minus mark of plus-44 and helped Boston reach the semifinals. The next year he set career highs with 18 goals and 60 points and was a participant in the NHL All-Star Game.

Prior to the trading deadline in March 1986, O'Connell was traded to the Detroit Red Wings for fellow blueliner Reed Larson. His offensive totals dropped as coach Jacques Demers utilized him as a penalty killer and defensive stabilizer on his disciplined squad. O'Connell adapted well to his new team and helped the Wings reach the semifinals in 1987 and 1988. After playing in his 13th season in 1989-90, the veteran defenceman retired.

Courtesy of the Hockey Hall of Fame