Saint Francis (17-12, 9-8 CL) was led by sophomore guard Josh Hogan's 18 points, while junior center Scott Kohne added 17.
Kohne reached the 1,000-point career milestone in the game, which made him the 31st Cougar to do so.
Kohne stands at 1,014 points, 27th on the list, and was the second Cougar to join the honored list this season. Earlier this season, Ethan Hussey became the 30th Cougar to score 1,000 or more points.
Hussey scored six against the Knights and currently ranks 20th with 1,116 points, 43 behind No. 19 Dave Moreland (1,159, 1976-79).
The Cougars led 37-34 with 15:05 to play after a Kohne bucket. However, they didn't score again until Hogan hit a free throw at the 10:02 mark. By then the Saint Francis advantage had evaporated after a 9-0 Knights' run that vaulted them to a 43-37 lead.
The Cougars never tied the game or led again.
Cougars senior Kevin Bloom hit two free throws with 3:50 remaining to pull his team to within 55-53, but the Cougars got no closer.
Marian (16-11, 8-9) went on an 8-2 run hitting six free throws.
Hogan scored at 2:56 halting the Marian surge momentarily, but the Cougars missed three shots in the time remaining.
The Knights swept the regular-season series having won the first meeting 67-65.
Nick Achille led Marian with 17 points, while Dwight Cliff and Jason Riley scored 16 points apiece. The victory was the Knights' fourth consecutive over the Cougars.