Marvin Cruz led the attack with 16 points including six crucial ones in the fourth quarter while Abe Santos, Nestor David and rookie transferee Axel Doruelo added 10 apiece as the Maroons sealed a second straight win.
"It was all about heart," said UP coach Lito Vergara, who won for the first time against the defending champion in two years.
Defense, however, spelled the difference for the Maroons as they held the Archers to a total of 56 points several days after the latter routed the Ateneo Blue Eagles, 78-60, at the Big Dome.
"We know that if we’re going to beat La Salle, we need to play tough defense and we did just that," said Vergara.
Former Archers Mika Vainio, Micharl Gavino and Michael Padolina were also instrumental as the three combined for eight points, 11 boards and manned UP’s interior defense that unnerved La Salle’s big men.
Earlier, University of the East, a surprise semifinalist last year, turned back a hard-fighting National University, 71-64, to notch its first win in two starts.
Earl Saguindel and Jorel Canizares paced the Warriors with 12 points each while the Bulldogs were led by Edwin Asoro’s 18 and Jonathan Fernandez’s 16 points in their second defeat in a row.
La Salle dictated the pace early as it raced to a 15-10 lead but UP struck back hard with a choking defense as the lead and momentum slowly shifted to the Maroons side going into the break.
From there on, it was all a UP show as its defense went to work against a La Salle squad missing Mark Cardona and Jerwin Gaco, their leading scorer and rebounder last year who are now turning pro.