The 511 Johnson, who traces his roots in Lipa, Batangas, finished with nine points, eight rebounds, seven assists and five steals. He scored the winning basket in the final 7.6 seconds and swatted Mark Macapagals desperate buzzer-beating attempt for the ICTSI Archers fifth win in nine outings.
John-O absorbed its fifth setback in nine games.
In the other game, Montana Pawnshop unloaded a 19-2 bomb in the third quarter and went on to beat Cheese Balls-Shark, 92-81, and boost its own semis bid.
With its 5-4 record and a tie with ICTSI in the lower half of the elims, Montana slammed the door on Cheese Balls.
John-O appeared headed toward victory as Macapagal and Jeff Napa fired three consecutive triples in a 10-2 blast that turned a 72-79 deficit into an 82-81 edge with exactly a minute left.
Ranidel de Ocampo regained possession for John-O following Joseph Yeos miss but also muffed his attempt in the ensuing play.
Bruce Dacia grabbed the rebound and Johnson made it 83-82, 7.6 seconds left.
In the return play, Macapagal was all set to take the last shot but Johnson tapped the ball out of his hands shortly before the final buzzer.
Mark Cardona topscored for ICTSI with 24 points, six rebounds and four assists while Reynel Hugnatan added 15 points, nine rebounds and three assists.
Dacia and Yap delivered 14 and 11 points, respectively.