Mater Dei won a coin toss and will play host to Riverside Poly on Tuesday in the second round of the Southern Section 5-A baseball playoffs.
The Monarchs are attempting to become the first school in Southern Section history to win football, basketball and baseball titles in the same season.
Irvine also won a coin flip and will play host to Riverside Arlington in the 4-A playoffs Tuesday. The key game in the division will be Canyon at Fullerton.
Tuesday's playoff games involving Orange County teams (all games begin at 3:15 p.m.):
Diamond Bar (25-1) at Fountain Valley (16-12); Royal (18-7) at El Dorado (21-5); Riverside Poly (20-6) at Mater Dei (22-4); Bishop Amat (20-5) at Cypress (14-12-1).