Pingris, one of the few remnants of the last years Challenge Cup champion team, had a monster game with 19 points, 20 rebounds, three steals and two shotblocks.
He dominated John-Os frontline duo of Ranidel de Ocampo and Ricky Calimag, who only combined for 19 markers and 10 caroms, to personally prevent the Senators from eventually joining the Hapee Teeth Sparklers (7-2) in the semis.
Welcoat blanked John-O in the final three minutes to notch its fourth win against five setbacks.
In the other game, LBC Batangas went to Froilan Baguion in the fourth quarter as it survived a late surge by Montana, 87-84, to enhance its own semis bid with a 4-5 slate.
"We played a team game with Marc Pingris leading the way," said Welcoat coach Leo Austria.<