The Blades have made a double loan swoop ahead of Tuesday night's trip to Walsall to ease the defensive crisis.
Versatile Blackpool defender Matt Hill joins United until the end of the season, whilst Sunderland youngster John Egan, who operates as a centre-back, is poised to stay in South Yorkshire for the next 28 days.
Hill, 30, who made close to 200 appearances for Bristol City, more recently played at Barnsley, before signing for Ian Holloway's men last summer. At Bloomfield Road, Hill has featured on five occasions this season, the most recent coming in October against West Ham United at Upton Park.
Meanwhile, 19-year-old Egan, who recently was named the Republic of Ireland's Young Player of the Year, joined Sunderland from Cork City in 2009. This season the defender has captained the Black Cats second string, in addition to being on-loan at Crystal Palace, where he played in the FA Cup.
Both are available for Tuesday's match at Walsall.