Maguire, 18, was shown a straight red card during Saturday's 3-2 win over Bristol City - only his second start for the Blades.
Neill Collins is expected to replace Maguire at the heart of defence alongside on-loan Aston Villa man Shane Lowry, although Rob Kozluk provides manager Micky Adams with another option.
Midfielder Lee Williamson is set to start again after he was taken off in the second half against Bristol City in order to protect his troublesome back.
Adams is not expected to make too many other changes. Midfielder David McAllister marked his full debut on Saturday with a fine goal and should continue alongside Nick Montgomery in central defence, while teenage striker Jordan Slew scored his second goal in successive matches following his full debut in the previous match at Preston.
The Blades must win at promotion-chasing Reading and hope fourth-bottom Crystal Palace fail to beat Leeds if they are to maintain their slim survival chances.
Source: PA
Source: PA