Both teams now have 20 points each from eight matches and a same goal difference (+13) but Mohun Bagan are ahead having scored more goals (16), compared to East Bengal's 14.
While all eyes were on Acosta, it was a 21-year-old Pintu Mahato from the erstwhile Maoist hotbed Jangal Mahal area in West Midnapore district who took the spotlight drawing the first blood with his bullet like shot in the 20th minute.
A product of Mohun Bagan's youth system, Mahato converted Arijit Bagui's cross from the right with precision, as East Bengal looked in disarray.
Mohun Bagan showed mobility in the midfield and another lesser known player, Bagui, who was roped in from Kalighat MS, assisted in their second goal scored by Henry Kisseka in the 30th minute.
Receiving the ball from Bagui from the right-flank, the Ugandan unleashed a ferocious drive that beat both Acosta and Mehtab Singh to hit the back of the net.
Having re-arranged their central defence to accommodate Acosta, East Bengal's defence struggled before Acosta finally made his presence felt, scoring from a rebound off his second attempt in a goalmouth melee.
Laldanmawia Ralte finally restored parity with a curling corner by Lalrindika Ralte which was somehow saved by Shilton Paul but the former slotted the ball home from the rebound.
It was a lackluster day for Mohun Bagan star striker Dipanda Dicka, who is the league's leading scorer with seven goals, as the Cameroonian failed to find the target on several occasions.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)