Stepping up in the absence of an injured Jemal Vizcarra, Duncil presided over the Tigers breakaway in the second quarter that had the España-based cagers turning a 16-18 deficit into a 47-28 lead at the turn.
Jervy Cruz actually provided the backup to that big UST 31-10 run as he matched Duncils 10-point splurge in that stretch and went on to finish with 22 points and 10 rebounds.
"Hes become a changed man after our first game loss," said UST coach Pido Jarencio of his 23-year-old guard in Filipino. "Before, he couldnt hit his outside shots, now hes making the crucial ones."
He was referring to Duncils timely baskets that doused cold water on the Warriors repeated rallies as the Tigers roared to their second straight win in three games to tie their victim at second behind the unbeaten Ateneo Eagles (3-0).
The Tigers also shone in defense as they answered the Warriors full-court trap defense with a press of their own.
"My team and UE play the same type of basketball, we run and we press," said Jarencio, a UST alumnus himself who played most of his PBA years with never-say-die Barangay Ginebra.
"But our trap is different from theirs because we do it with more heart," he added.
USTs defense forced UE to turn the ball over 25 times, which the Tigers translated into 24 points. UE scored 16 points off USTs 19 turnovers.
Earlier, Adamson pounced on University of the Philippines pair of late game miscues to pound out an 85-83 victory and even its card to 2-2.
Ken Bono led the Falcons with 22 points while Patrick Cabahug added 18, including a basket with 21.9 seconds to go to give Adamson the lead for good.
Marvin Cruz, one of the leading UP scorers, was called for a backing violation and committed a foul away from the ball, resulting in two free throws plus possession for the Marcelino-based cagers in the closing seconds.
Marvin Poloyapoy and Cabahug, who was fouled by Ira Buyco in the ensuing play, nailed four foul shots in a row and sent the Maroons to their second straight setback against a win.
"The boys learned from our mistakes when we lost to Ateneo, my big men played smarter this time," said Adamson coach Leo Austria.