Chatsworth, which was 2-7 late in the season, has knocked off Granada Hills, University and Sylmar in its last three games behind running back Justin Santos, who was an all-league player as a sophomore and picked up 271 yards in 38 carries on Friday night in a 47-20 quarterfinal victory over No. 4-seeded Sylmar.

South Gate routed No. 3-seeded Eagle Rock, 30-7. Junior running back Lavelle Thompson had 168 yards rushing in 16 carries and scored two touchdowns. Another running back, senior Alexander Flatos, gained 148 yards, scored two touchdowns and had an interception.

Both teams face tough semifinal games. Chatsworth will play at top-seeded San Fernando, a 42-0 winner over Bell. Cristian Santos rushed for 149 yards and scored three touchdowns and passed for 144 yards and one touchdown. South Gate will play at No. 2 Granada Hills, which routed Grant, 37-6.

Neither team seems particularly concerned about being the underdog. Each program is having a revival under a new coach. Andrew Kim took over in 2011 at Chatsworth. Jose Casagran took over in 2012 at South Gate.

Eric.sondheimer@latimes.com