The host Blue Jays managed only five shots overall, including just two on goal, as they dropped to 1-4 on the season after being shut out Sunday by the Knights.
Jack Palen provided the only goal Wartburg (2-4) would need when he scored off an assist from Daniel Luzindya in the 79th minute. The Knights piled up a total of 24 shots, including 10 on goal, and had a 6-2 advantage in corner kicks.
Westminster junior goalkeeper Connor Bandre posted nine saves.