The Danville duel will happen next weekend.
Monte Vista defeated the Wolves, 34-33, in the final regular season game two weeks ago.
On Saturday night, the sixth seeded Mustangs held the lead most of the game over the third seeded Pirates.
Monte Vista led 7-6 at half. They scored two third quarter touchdowns to widen their margin to 21-6.
However, San Leandro crossed the goal line in the fourth quarter to cut the lead to 21-12 before Monte Vista put the game away with touchdown with less than a minute to play.
Monte Vista is now 8-4. They defeated Heritage High, 42-36, last week to reach the second round.
San Leandro finishes their season with a 6-5 record.