Steve Kittrick will be facing up to Ossett Town at home tonight in the Integro League Cup without departed assistant-manager Chris Bolder.
Bolder has taken over the vacant manager's job at North Ferriby United with immediate effect, bringing his four-year spell at Boro to an end.
He was initally signed by Rudy Funk from North Ferriby as a player, but after the appointment of Kittrick almost two years ago, he stepped up to being assistant-manager.
Kittrick said: "I wish Chris all the best and thank him for everything he has done at the club.
"This is the right move for him because it means he will be nearer to home and he has the opportunity to be a manager.
"I did expect it because I knew that their new owner Jamie Waltham was his pal and also Chris' brother Adam has just gone back there.
"There will be no immediate replacement, we will have a look at the situation and then see how things are."
Boro are at full strength for tonight's game and Kittrick will be throwing out a strong team at the Flamingo Land Stadium.
He added: "Everyone is available and we will be playing a very strong team.
"I would have treated it a bit differently had Saturday's game at Colwyn Bay been on, but we need to maintain our momentum.