Stating that the move by the Indian giants was unacceptable, Darby said in his resignation letter: “This has created a lot of mental pressure on me which I can’t accept.”
Mohun Bagan general secretary Anjan Mitra confirmed that Darby’s resignation had been received and that it would be accepted.
Derby was appointed coach four months ago replacing Subhas Bhowmick, but a poor recent Federation Cup had seen extra pressure being piled on the Englishman's shoulders.
However, the appointment of a three-member technical committee comprising of Olympian Chuni Goswami and former internationals Prasanta Banerjee and Satyajit Chatterjee, proved to be the final straw for Darby who has previously coached in Australia, Malaysia, Singapore and Thailand.
Darby is reported to have met the Mohun Bagan players on Saturday to inform them of his decision, telling ESPNSTAR.com that throughout his stint the Mohun Bagan players "had been excellent in both their attitude and their professionalism".
In the wake of Darby's departure, Mohun Bagan have moved quickly to make Nigerian Bernard Operanazie, who was an assistant under Darby, the club's acting coach.