Rutgers (15-11, 5-8) also got 15 points from Anthony Farmer. The Scarlet Knights won for the third time in 10 games.
Douby scored 18 first-half points, including seven during a 17-4 run to put Rutgers ahead 35-21 at halftime. His 3-point shot seven minutes into the second half extended the Scarlet Knights' lead to 45-27.
McHugh Mattis completed a 9-1 run with an in-close basket that got South Florida within 46-36 with 8:40 left. Rutgers responded by scoring the next six points, including two free throws by Douby that started the stretch.