The England defender was initially suspended for United's 2-1 defeat to Leeds United on Monday after being dismissed in the Premier League clash with Bournemouth on March 20. However, an independent regulatory commission has now extended his punishment after charging him over his behaviour towards the fourth official following his sending-off.
The Football Association said in a statement: "It is alleged that the defender acted in an improper manner and/or abusive and/or insulting words and/or behaviour towards the fourth official following his dismissal."
Maguire admitted the charge and has been fined 30,000 pounds in addition to the extra suspension, ruling him out of the trip to Stamford Bridge.
United head coach Michael Carrick will also be without Lisandro Martínez, who was sent off against Leeds for pulling Dominic Calvert-Lewin's hair in a decision Carrick labelled "shocking." The club have appealed the Argentine's suspension, although there is little optimism it will be overturned.
The double defensive absence leaves Carrick facing a major selection issue, with a youthful centre-back pairing of Leny Yoro and Ayden Heaven expected to start. Matthijs de Ligt remains sidelined through injury, further limiting defensive options.
United go into the match holding a seven-point advantage over Chelsea in the race for Champions League qualification, but back-to-back defeats would reduce that gap to four points and intensify pressure ahead of the trip to Stamford Bridge.