Trewin made a splash in his first season as a starter for Michigan Tech, helping the team win the
WCHA regular season title while allowing the fewest goals in conference. He was named to the All-WCHA first team and an All-American but could not stop 7th-place
North Dakota from scoring 6 goals in the opening round of the
conference tournament, ending the Huskies' season. MTU was expecting big things from their new starter in his second season, however, the team tumbled down the standings and Trewin allowed more than a goal per game more in 1972. Michigan Tech finished 7th in the standings but nearly upset
Wisconsin in the tournament, losing 7–9 on aggregate. Trewin continued to founder the next season, playing just 8 games before leaving the program when two other Huskies netminders began turning in better performances. Trewin made a few appearances for senior hockey teams over the next few years to see if he could recapture his form in 1971 but nothing came to fruition. ==Statistics==