Junior starting pitcher Crosby Slaught allowed two runs in seven innings to earn his sixth win in seven decisions this season, and senior Brian Hernandez got the final out for his 11th save after freshman Jimmy Litchfield tossed 1 2/3 innings of shutout relief.
It took three UCI pitchers to outduel UCR junior Eddie Orozco, who threw a complete game and struck out 11, but fell to 4-2.
After lashing 16 singles among its 18 hits in the series-opening 12-0 win Friday, UCI had four doubles among its nine hits Saturday. Two of those doubles drove in runs, including the game-winning RBI by D.J. Crumlich with one out in the eighth.
Crumlich's drive into the gap in right-center field plated junior second baseman Tommy Reyes, who opened the eighth with a single.
Crumlich, playing with a strained left shoulder that makes some swings painful, inflicted some pain on an Orozco slider, a pitch that had struck Crumlich out twice earlier.
Junior center fielder Christian Ramirez, who made a game-saving diving catch on a sinking liner to center to end the Riverside eighth, doubled in senior Drew Hillman, who had doubled to open the UCI second to give UCI a 1-0 lead, UCR shortstop Trevor Hairgrove hooked a two-run home run just inside the left-field foul pole to put the hosts (26-22, 8-12) on top in the third.
But Hillman scored the equalizer on a sacrifice fly by Ramirez in the fourth.
Riverside, which turned four double plays, three of which ended UCI innings, had runners at second and third with one out in the fifth inning.