A.J. Ramirez hit a three-run double in USC's seven-run ninth inning, and Kyle Twomey pitched into the eighth as the Trojans eliminated UC Santa Barbara with a 12-3 victory in the Lake Elsinore Regional on Saturday.
Twomey (8-2) gave up seven hits and three runs in 7 1/3 innings for the Trojans (38-20).
Leadoff man Bobby Stahel had three hits and scored three runs, and Garrett Stubbs had three hits and two RBIs.
Regional host UC Santa Barbara (40-17-1) exited the tournament without ever holding a lead in its second NCAA tournament appearance since 2001.
Trailing, 5-1, in the eighth, the Gauchos scored twice and had the bases loaded but USC reliever Tyler Gilbert, inheriting a 2-0 count, struck out pinch-hitter Billy Frederick to end the rally.
USC, which has one loss in the tournament, will face San Diego State on Sunday. The winner of that game will go to the regional final.
This is the Trojans' first NCAA regional postseason appearance since 2005.
Virginia 3, San Diego State 1: Ernie Clement hit a go-ahead RBI single in the eighth inning and the Cavaliers picked up another run in that inning when Daniel Pinero was safe at first on a throwing error by the Aztecs' Alan Trejo, allowing Adam Haseley to score.
—Times wire reports