FC United of Manchester require a second attempt to kill off the Northern Counties East League club following the weekend draw.
Marginson says his players reverted to long ball tactics - and that is not what they were told to do.
But despite saying words were had after the game, the manager says the players have his backing.
"We were really nervy and it gave them a fighting chance. We gave away our advantage by planning the style of football that wasn't asked of them," Marginson told the club's audioboom service.
"We have to shape up and in the replay we have to pass the ball because that's why they are here. It's down to them to take instruction on board.
"On another day, our chances go in. But we are going through a tough time of it at the moment.
"I back the boys publically a lot of the time but they have had some home truths in the changing room.
"They aren't making it easy on themselves but we will stick by them. I have told them there's no pressure but they need to play the type of football that's going to win us the match on Tuesday."