In a match that had several twists and turns, Mohun Bagan took a lead through Cornell Glenn (26th and 45+1st) but only to crumble under pressure as Derrick Pereira's side showed a lot of promise through a double strike from Juan Quero Barasso (30th and 33rd).
Haitian forward Sony Norde returned to the playing XI and revived the home team's hopes with his 42nd minute strike before Glenn made it 3-2 in an action packed first-half but it was the Pune outfit's Cameroonian recruit Aser Dipanda who gave the thousands of Mohun Bagan fans heartbreak with his 75th minute strike.
Mohun Bagan pressed hard for the winning goal but only to return luckless as they would rue Norde's 27th minute strike which seemed to be a goal as Subrata Pal saved the shot apparently from inside the goal-line.
Earlier, after being set up by substitute Jeje Lalpekhlua, Glen scored on the rebound to give the home side the lead in front of a rousing support.
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A minute later, they almost doubled the lead with Norde firing a shot from the left and goalkeeper Pal latching on to the ball.
Adding to the misery, the Shivajians equalised in the space of four minutes with Quero scoring from a Douhou Pierre pass, beating an advancing Debjit Majumder.