Sen also took potshots at the East Bengal coach Khalid Jamil who took charge of the Kolkata side after guiding Aizawl FC clinch I-League title last season.
"We should have won by five-six goals. (Ansumana) Kromah missed two, (Aser Pierrick Dipanda) Dicka missed two, if refereeing was better, we would have got a penalty in the first-half," Sen said at the post-match news conference.
Mohun Bagan dominated the match but only to win by a solitary goal which came off a header from their Nigerian central-defender Eze Kingsley in the 40th minute.
East Bengal came close to scoring once in the 80th minute but Mohun Bagan goalkeeper Shilton Paul put up a fine save to deny Laldanmawia Ralte.
More From This Section
"Coaches say they undertake video analysis and all that. God only knows what they do," Sen said, without taking any name but clearly referring to his opposite number.
He said Mohun Bagan can beat any team if they play to their potential.
"Winning the I-League Trophy is our priority and to get it with a victory over East Bengal is all the more a satisfying feeling," he said.
For man-of-the-match Kingsley, it was his first goal of the I-League and it could not have come on a better occasion.
"To score it in a derby is the best thing to happen. We fought for it and we got a goal. It's like a dream come true for me," the 26-year-old Nigerian central defender said, dedicating the goal to his mother.
"I'm not saying my players did not give 100 per cent today, but in East Bengal colours, you have to give it a 100 per cent every time.
"It was a silly goal to concede. The marking for the goal was very poor. (Willis) Plaza has to work hard, has to concentrate on next match," Jamil said about his Trinidadian forward Plaza who was at his profligate best today.