Michel Mongeau attracted the attention of major junior scouts while playing for the Lac St. Louis Lions in AAA midget where he recorded 45 goals and 102 points in 48 games at the age of 16.
The next season he joined the Laval Voisins. In 1983-84 he contributed 94 points which would normally seem like a lot but in the high-scoring Quebec League, it landed him just sixth in scoring with the team. The leading point getter that year for the Voisins, and the entire league, was 18-year-old Mario Lemieux, who recorded an astonishing 282 points. Laval was the cream of the crop in the QMJHL and they represented the league at the Memorial Cup. Despite having dominated in Quebec, the team was unable to get on track at the Cup. In the opener they were humiliated 8-2 by the Kitchener Rangers. They improved considerably in their second outing but still came out on the short end of a 6-5 score at the hands of the Ontario champion Ottawa 67s. Kamloops of the WHL knocked them off 4-3 in the third game, eliminating Laval from the tournament.
Mongeau remained in Laval for another two years and despite having a 180-point season in his last year, was undrafted by any of the NHL teams. He signed a free-agent contract with the Saginaw Generals where he had a great offensive season, collecting 95 points in 76 games. The next two years were tough physically for Mongeau who underwent four hernia operations and a knee procedure.
His big break to the NHL seemed to come in the form of a free-agent contract offered by the St. Louis Blue in the summer of 1989. The bulk of his season was spent with Peoria of the IHL but he was called up as an injury replacement for seven games that year and he had six points. He broke the lineup another 36 times in 1991-92 but never seemed to manage to convince the Blues' brass that he could hold down a regular spot in the lineup.
Mongeau was left exposed by the Blues in the 1992 NHL Expansion Draft and he was claimed by the Tampa Bay Lightning. He played just four games in a Lightning uniform before being traded in a package deal to Quebec along with Martin Simard and Steve Tuttle for Herb Raglan. The move did nothing for Mongeau's NHL career though. The Nordiques could not find a spot for him on their roster and he never played for them, and in fact never played another game in the NHL.
Following short playing stints in Italy and Switzerland, Mongeau returned to Quebec for the 2000-01 season where he played Senior A hockey. Mongeau always said that thinking about retirement would be the toughest part of hockey. That and the pressure that came when traded to another team.
Mongeau certainly faced his share of physical misfortune which definitely slowed down the potential for a stronger career, but the worst happened during a game in 1993-94 in an incident while playing in the IHL with Peoria. Mongeau was cross-checked hard from behind by Cleveland's Chris Tamer. He was catapulted head-first into the goal post, resulting in seven facial fractures. He now has three metal plates in his face. He had his jaw wired shut for a month and forced him out of hockey for a year. Mongeau sued Tamer, but the first trial ended in a mistrial. At the second trial, few of the original witnesses were available and the case was lost, being deemed an accident.
Despite a natural ability to score, the combination of injuries and an inability to fit in with specific systems of the teams he happened to be on at the time, limited Mongeau to just 54 NHL games where he had six goals and 25 points.