Dylan Mines scored two goals and picked up an assist for the Warriors, who fell to 3-4 on the season.
Liam Rudd also scored for WMC, while Evan Fles had an assist.
Plainwell scored the game-winning goal on a corner kick with 40 seconds left in regulation.
“We play non-conference games against teams in divisions higher than us to prepare for the tournament,” said WMC Coach David Hulings. “This game can be a great teaching tool for this season.”