Ralf Rangnick has been linked with a move to Old Trafford, where United manager Erik ten Hag has hinted that the Red Devils captain should be included in the players' vote.
McGuire is set to make a world-record move for a full-back five months after leaving Leicester City for 80 80million after leaving Ashley Young for Inter Milan in January 2020.
England international McGuinness is under scrutiny for both his performances and captaincy, and United are still struggling in the Premier League and the Champions League.
United are sixth in the league with little chance of qualifying for the Champions League, six points behind fourth-placed Arsenal, who beat Rangnic 3-1 on Saturday.
Ajax boss Ten Hag is preparing for a major rebuild, with the future of Cristiano Ronaldo and Paul Pogba still in question and their contracts at Old Trafford set to expire.
One of the first things the Dutchman has to do is decide the leader in the locker room, and Rangnic advises United players to vote on who should be their next captain.
Asked if McGuinness would retain the captain's armband next season, Rangnick told reporters: "I understand your question, but I do not know what kind of players will be here and I understand what the team looks like.
"What I did when I was the head coach or manager was what I called the German captain Mannschaftskapitan.
"I firmly believe that the team manager should choose the captain, and we have always done that.
"We have a board of four or five players, which is called the Spirits, and the player who gets the most votes is ultimately the captain. That's what I did.
"I know a lot of coaches don't do that. That's what I have to do next season as a manager. But in the end, I'm not. That's up to Eric. "
The appointment will be a key factor in United's rejuvenation. Rangnic, who previously worked as a consultant with Ten Hag, has demanded some verdicts in the transfer cases.
Rangnic expressed his excitement as he teamed up with Ten Hag to try to turn around United's fortunes next season.
"There is a lot that can be improved," he said. You will get better with a new manager. "I firmly believe that we will come with new players and new strength in that team."
"With the new players and the quality of the players already here, I'm very good that we will be much better next season.
"I look forward to working in the advisory role and it is clear that Erik is helping as much as she wants.
"In my last two clubs, A player has never signed without the manager's permission. That must have been the case with Eric.
"Eric will give some advice, and possibly with the board and the scouts, and I will be positive about deciding the right players.
"Obviously, I'm willing to help Erik and everyone at the club prepare to change everything for the better."
However, former RB Leipzig coach Rangnic has yet to speak to the upcoming Ten Hag due to the promises made by Ajax and Ajax.
"Ten Hag's focus is now on Ajax, who are trying to win trophies there. "My focus for the next few weeks is on our team to get the best possible results."
"Every time he has time or wants to talk, yes, I have, but now I do not want to contact him with my personal account."