Making his way up through the minor hockey program of Thunder Bay, it was not long before Trevor was demonstrating the skills that he had inherited from his father Bill "Red" Johansen, a member of the 1948 Memorial Cup winning Port Arthur West End Bruins and minor pro player. A top player with the Thunder Bay Hurricanes junior team, Trevor was a part of their USHL victory in 1974, before making his way to the Toronto Marlboro Major Junior A Hockey Club being selected in the first round draft.

In his first year with the Marlies, Trevor was a stand out on defence, living up to his nickname 'Block'. The 1974-75 season proved to be an exciting one for Trevor as he joined his father as a Memorial Cup champion. A two time Ontario All-Star, he won a silver medal with the Canadian juniors at the 1977 world championships. After three seasons with the Marlies, Trevor was ready for his next step in the life of a young hockey player - the NHL draft. Trevor's outstanding defensive skills had not gone unnoticed being selected the number 12 draft pick in the first round of the 1977 draft by the Toronto Maple Leafs.

Unlike many young players Trevor did not have to spend time in the minors before joining the Leaf line up. A regular on the Leaf defence during his rookie year, his style of play earned him praise from coach Roger Neilson who noted that the most impressive feature about Trevor was his consistency and his ability to play at a steady level. Many veteran hockey observers compared Trevor's style to that of hockey great Tim Horton. After close to two seasons with the Leafs Trevor was traded to the Colorado Rockies with Don Ashby for Paul Gardner.

Following time with Colorado and the Los Angeles Kings Trevor returned to the Leafs in the 1981-82 season. Plagued by a recurring knee injury, Trevor retired in 1982 with an NHL record of 286 games played, 11 goals and 46 assists in five seasons. Aside from his NHL involvement, Trevor also had the opportunity to represent his country as part of Team Canada in 1979, not only lending his defensive skills, but scoring the third period tie-breaker goal against Finland allowing Canada to move into the playoff finals, demonstrating yet again his outstanding hockey skills.

Inducted into the Northwestern Ontario Sports Hall of Fame, September 27, 1997