Captain Sonny Bradley and Rhys Norrington-Davies keep their place in defence, whilst there is a first competitive start for Peter Kioso at right-back, who makes a first appearance at the Kenny, the only change from the side that beat Reading in the Second Round.
Tom Lockyer is the fourth man in defence - also his first start at home for the Hatters - as James Bree misses out with an injury sustained on Saturday against Derby County.
After scoring the winner against the Rams at the weekend, Jordan Clark starts alongside Kazenga LuaLua and Danny Hylton in the forward positions.
Town: Shea, Kioso, Bradley (C), Lockyer, Norrington-Davies; Tunnicliffe, Shinnie, Moncur; Clark, LuaLua, Hylton.
Substitutes: Sluga, Cranie, Pearson, Cornick, Lee, Mpanzu, Collins.
Manchester United: Henderson, Wan-Bissaka, Bailly, Maguire (C), Williams; Matic, Fred, Van de Beek, Mata, Lingard; Ighalo
Substitutes: Grant, Rashford, Greenwood, Fernandes, Dalot, James, Mengi.
Referee: Tim Robinson