Maguire was shown a straight red card by referee Stuart Attwell in the 78th minute of United's 2-2 draw at Bournemouth on March 20 for denying Evanilson a clear goalscoring opportunity. He served the first game of that ban during Monday's 2-1 home defeat to Leeds United. The additional ban follows a separate FA charge relating to his conduct towards fourth official Matt Donohue as he left the pitch.
According to the hearing findings released on Wednesday, Donohue reported that Maguire said to him: "You're a joke. You're all a f***ing joke."
Maguire denied directing those words at any official. In his own account, he stated: "I did not use abusive and/or insulting words towards the fourth official or any other match official. As I left the field of play following my dismissal I said something along the lines of 'it is a f***ing joke'. I am certain that I did not call the Fourth Official or any Match Official, a joke or use any other form of insult."
The independent regulatory commission found against him. He was handed a one-game ban for the improper conduct and fined £30,000.
The timing could hardly be worse for interim manager Michael Carrick. Lisandro Martínez faces a three-match ban of his own after being sent off for pulling the hair of Dominic Calvert-Lewin during the Leeds defeat, though United have appealed that decision. If the appeal fails, Carrick could be forced to field Leny Yoro, 20, alongside Ayden Heaven, 19, at centre-back against a Chelsea side sitting third in the table.
United are currently sixth and victory at Stamford Bridge would significantly boost their Champions League qualification hopes.