Though the Golden Tigresses cruised through the first two sets, they faced stiff resistance from the Fighting Maroons in the third frame.
Down 9-14, UST leaned on the powerful hitting of Regine Jurado and the precise playmaking of setter Cassie Carballo to stage a comeback, capitalizing on UP's errors late in the set to seal the straight-set victory.
The win not only secured the top seed for UST but also pushed UP to the brink of elimination with an even 3-3 record.
Kianne Olango and Niña Ytang tried to keep UP in contention, but costly errors in the closing stages of the third set hastened the team's downfall.
"We're working on our maturity, decision-making, and judgment, those things. Kasi 'yung skills ando'n na eh. We're enhancing them naman sa training, so we need namin 'yung avenue like V-League na malaking opportunity lalo na sa rookies," said UST head coach Kungfu Reyes.
Jurado finished with seven points, including a key attack that cut the third-set deficit to 12-14, while UAAP Season 86 Rookie of the Year Ange Potos led the charge with 15 points.
Carballo also delivered, notching 12 excellent sets and adding four points.
UST will aim for a sweep of the eliminations when it faces Letran tomorrow at noon.
No player from UP reached double digits, with incoming rookie Olango leading the way with eight points and Ytang contributing seven.
UP’s playoff hopes now depend on the outcome of the ongoing match between College of Saint Benilde and Lyceum of the Philippines University.