Fresno State (40-15) committed two errors in the opening inning and four in the game as UCI All-American starter Matt Summers won his fifth straight start and improved to 11-2.
Leyland, who hit two home runs and drove in five runs in four games to earn all-regional honors last season at UCLA's diamond, was two for four to help the Anteaters advance to the winner's bracket clash against San Francisco (33-23) Saturday at 6 p.m.
The Dons scored a 3-0 win over top-seeded UCLA (34-23).
Junior shortstop D.J. Crumlich and junior second baseman Tommy Reyes both went three for five with one RBI and junior catcher Ronnie Shaeffer was two for four with three RBIs for the Anteaters. Shaeffer, who leads the nation in throwing out would-be base stealers, nailed the only Bulldogs runner attempting to steal.
Senior Brian Hernandez was two for five as UCI amassed 15 hits, 12 against Gonzalez, who had not given up more than nine hits or more than three earned runs in any of his 15 previous starts this season.
Fresno State, which came in with 50 home runs, did not manage an extra-base hit.
Summers, who had given up two combined hits in his last two regular-season starts, both complete-game shutouts that included a no-hitter against Long Beach State, allowed three runs, just one earned, on five hits in six innings. Summers walked one and struck out six. He threw 104 pitches.
A would-be double-play grounder skipped through the shortstop's legs and Gonzalez dropped a relay throw to first after an out at second base to prolong the first inning. Leyland's home run was in the glove of leaping right fielder Dusty Robinson, before it fell over the fence for his fourth dinger of the season, his first opposite-field blast in 2011.
It was the 12th big fly this season for the 'Eaters, who are now 11-0 in games in which they have gone yard.