At the halfway stage after eight rounds, Mohun Bagan are the only team to maintain an unbeaten record with 18 points from eight games with five wins and three drawn games. They are three points clear of second placed Benglauru FC, who are on 15 points with equal number of wins.
Katsumi's 73rd minute strike from a Sony Norde centre proved to be the difference in a match where Goan side gave Mariners a tough time but it was their young goalkeeper Debjit Majumder who thwarted each of their attempt with an impressive performance under the bar.
The goals were hard to come by even as both the teams pressed hard and it was Debjit who should be credited for keeping a clean slate for the defending champions.
In a 13th minute move, Odafa beat Mohun Bagan defenders Raju Gaekwad and Kingshuk Debnath before unleashing his powerful rightfooter but Majumder stayed rock solid.
Odafa's best chance to score was minutes after conceding goal when Majumder charged out of his his line but the Nigerian's shot hit the body of Majumdar.