Vasco Sports Club, Goa, kept their title hopes alive by exploiting a sloppy Mohun Bagan defence to fashion a 3-2 victory in a seventh National Football League match at the Salt Lake stadium in Kolkata on Wednesday.
Brazilian Marcos Pereira scored twice and Angelo Gomes got the other goal as the Goa side took a commanding 3-0 lead at half-time.
Bagan reduced the margin through Sunil Chetri and Baichung Bhutia in the second session.
The teams had drawn 1-1 in the first leg in Goa.
The Bagan defence put up a lacklustre show, leaving gaping holes, and each of the Vasco goals resulted from the ineptitude of the local side's rearguard.
On the other hand, Vasco custodian Rogerio Ramos stole the show with a fine display, as he thwarted the Bagan strikers, including Jose Barreto, on several occasions.
The result bolstered second-placed Vasco's points tally to 34 from 18 matches. Though way behind leaders East bengal, they still have a chance of claiming the title.
Bagan, who have had a dismal season, winning only the All Airlines Gold Cup, remain on 29 points from 18 games.
Pereira put Vasco ahead in the 15th minute and increased the lead six minutes later.
Pereira made it 3-0 in the 40th minute.
Chetri pulled one back for the defending champions in the 31st minute of the second-half while Bhutia reduced the margin further in injury time.