Mumbai take lead
Mumbai did not have to wait long to take the lead. Issoko was the architect, twisting and turning past Mandar Rao Desai before picking out Bastos' run at the far post in the 20th minute.
The Brazilian, left unmarked, turned it in first-time past a hapless Naveen Kumar.
Goa equalise
The goal jolted Goa into action and they equalised just past the half an hour mark.
Corominas found some space to shoot, but his effort was saved by goalkeeper Amrinder Singh but a lurking Jackichand pounced on the rebound.
Turning point
In the 39th minute, the tie turned on its head as a low corner from Brandon took a touch off Corominas and found Fall who stooped down and sent a header home to hand Goa the lead.
Mumbai thought they had an equaliser just before half-time when Bastos saw a shot spilt by custodian Naveen Kumar. Sougou reacted fast and turned it home but was deemed to be off-side.
Further downhill
It all went further downhill for Mumbai after the break as Goa turned on the style and pumped three more goals past Amrinder.
Six minutes into the half, Corominas was left unmarked by a poor Mumbai defence to head home Jackichand's cross at the far post.
Fall added another when he got his head to a corner, yet again, ahead of Mumbai defenders. The Gaurs went on to pepper the Mumbai goal with a flurry of shots following that goal and only a combination of Amrinder and the woodwork saved Mumbai from going further behind.
But the fifth goal did come in the 82nd minute when Hugo Boumous slipped in Brandon who slid a shot in past Amrinder to pile a heap of misery on Mumbai City FC.