Second-seeded USC finished 37-19 overall and 18-12 in Pac-12 Conference play.
Third-seeded Virginia (34-22) is making its 12th consecutive regional appearance. The Cavaliers finished 15-15 in the Atlantic Coast Conference.
Santa Barbara (40-15-1) is making its second regional appearance in three seasons. The Gauchos were 16-8 in the Big West Conference.
San Diego State (40-21) won the Mountain West Conference tournament. The Aztecs were 20-10 in conference play.
The regional champion advances to a super regional against the winner of a regional hosted by UCLA (42-14), the top-seeded team in the tournament.
Super regional winners advance to the College World Series in Omaha, Neb.