However ATK still remained on top with 12 points. The Pune franchise, who travelled without their French World Cup winner David Trezeguet, stunned one and all as their East Bengal recruit Dudu repaid his coach's faith with a well directed header in the 31st minute to silence the crowd.
Till then, ATK who were bolstered by the return of mercurial forward Fikru Teferra and manager Antonio Habas off the field impressed with their passing and had the better share of possession against Pune's defence that looked weak.
But the day clearly did not belong to the league leaders who had two howlers early on with their top two striking duo - Fikru and Borja Fernandez - missing one each. Having seized the momentum thanks to Nigerian's strike, Kostas Katsouranis made it 2-0 after the break when the Greek World Cupper used his outstep to curl one away as goalie Subhasish Roy Chowdhury looked in absolute disbelief.
ATK finally made their presence in the scoresheet in the 84th minute after Pune goalkeeper Arindam Bhattacharya felled Fikru in an inexplicable manner as the Ethiopian converted from the spot without much fuss.
Pune got a free-kick at the edge of the box when Josemi pushed Dudu from behind as Davide Colomba converted the shot with a leftfooter that took a Kingshuk Debnath's deflection to hit the back of the net to sink ATK's fortunes.