With the win, the Mavericks even their record to 4-4 overall and 2-2 in region play. Riverside falls to 1-7 overall and 0-4 in the region.
It was the 16th straight region loss for the Warriors, who are in their third season in Class 4A.
In other Region II-4A action, Byrnes, ranked No. 1 in the state and in the top five nationally in two major polls, was stunned by Gaffney, 22-18, at The Reservation in Gaffney.
Byrnes (7-1, 3-1) defeated Gaffney (5-3, 3-1) in last year's Class 4A state championship game.