Marquette (16-3, 8-1 C-USA American) posted its eighth straight victory and stretched its home winning streak to 27 games. Marquette's Dwayne Wade has held to just seven points, only the third time he has failed to reach double figures in 51 career games. All three of those games have come against St. Louis.
But Diener helped pick up the slack, getting the best of his older cousin, Drew, who is a senior for the Billikens.
After Travis Diener's driving layup made it 67-61 with 37 seconds left, St. Louis (7-11, 1-6) answered on Josh Fisher's three-pointer with 21 seconds to go.
The Billikens got back the ball when Marquette threw away the inbounds pass. St. Louis set up for possible game-tying three-pointer, but was unable to get off a good shot as the heavily-guarded Fisher launched an off-balanced jumper from the left wing that missed the rim.
Wade clinched the win by hitting one of two from the line with 5.8 seconds remaining.
Chris Sloan and Marque Perry scored 13 points apiece for the Billikens.