Mohun Bagan defeated Oil and Natural Gas Corporation 5-1 in their opening Group II quarterfinal league match of the 122nd Durand Football Cup in New Delhi today. Surkumar Singh and Nigerian Chidi Edeh struck twice while Jose Barretto scored once for the Kolkata giants. For ONGC Chukwuma Udofia pulled one back in the 82nd minute. Mohun Bagan, who finished runners-up in the IFA Shield last week in Kolkata, now need just a draw against JCT in their last quarterfinal league match on Friday to make it to the semifinal as Group II toppers.br/br/ONGC, on the other hand, are out of the tournament as they had lost their opening match against JCT 0-1.