The game turned on execution down the stretch, as the Anteaters (9-11, 3-5 in conference), failed to produce a field goal in the final 7:01.
Michael Hunter’s three-pointer with 7:01 left put the hosts up, 51-48.
A Darren Moore free throw created a 52-52 deadlock with 4:19 remaining, but Riverside scored the next four points.
The Highlanders (8-11, 2-5) also finished the game on an 8-0 run to break a five-game losing streak.
Hunter, who was kneed in the spine in Thursday’s home win against Long Beach State, had been the leading pain in the Highlanders’ side until the final moments.
The lithe, 5-foot-10 senior guard had hit seven straight field-goal tries, including four straight from three-point range, before missing his final attempt, a five-foot runner that wedged between the rim and the glass with 47 seconds left and Riverside leading, 59-56.
Hunter finsihed seven for 11 from the field, four of six from beyond the arc.
UCI committed four turnovers in the final four minutes to sabotage its attempt to continue its home dominance over Riverside.
“They made some key baskets down the stretch and we weren’t able to convert,” Douglass said. “[Kyle] Austin [a 6-8 junior forward] made some big buckets for them and their guards did a good job of attacking. I was not happy with our perimeter defense.”
Austin, whose 16.8 scoring average coming in was nearly double the Highlanders’ second-best scorer (Larry Gurganious at 8.6), scored 16 of his 18 points after halftime.