Ole Gunnar Solskjaer's side lost their 2020-21 Premier League opener at home to Crystal Palace on Saturday, whereas Luton have made an excellent start to their new Championship season, recording two wins from two games.
Luton will certainly be the underdogs heading into Tuesday's contest, but there is no question that the Hatters will be feeling good about themselves after an excellent start to the 2020-21 season.
Nathan Jones's side have already played twice in the EFL Cup this term to advance to this stage, beating Norwich City 3-1 at home on September 5 before recording a 1-0 victory at Reading on September 15.
It would be fair to say that the team will have one eye on their next league game against Watford on September 26, but the chance to dump United out of a cup competition does not come around too often.
Tuesday's clash will actually be the first meeting between these two teams since April 1992, when the points were shared in a 1-1 draw, while Luton have lost eight of their last 10 games with United.
United, as mentioned, will enter this match off the back of a disappointing 3-1 home defeat to Palace in their 2020-21 Premier League opener at Old Trafford.
New signing Donny van de Beek came off the bench to register for the Red Devils late on, but a poor performance from Solskjaer's side saw them lose on the opening weekend.
Solskjaer reiterated the importance of improving the squad after the match, but the team must recover quickly as they will face Luton on Tuesday before continuing their Premier League season away to Brighton & Hove Albion on September 26.
United have won this competition on five previous occasions, the last of which was in 2016-17; they reached the semi-finals of last season's EFL Cup but lost on aggregate to eventual winners Manchester City.
The League Cup is certainly down the club's list of priorities this season, but there is no downplaying the importance of the match to a side looking to feel their way into a new campaign.
Luton EFL Cup form: WW
Luton form (all competitions): WWWW
Man United form (all competitions): L
Tom Lockyer should be available after a bout of cramp, though, and the team is expected to have a similar look to the one that faced Reading in the last round of the competition.
As for United, there are expected to be wholesale changes from the side that started against Palace, with Dean Henderson, Eric Bailly, Brandon Williams and Odion Ighalo all likely to come into the side.
As a result, there is likely to be a spot in the squad for 18-year-old centre-back Teden Mengi, who is now training with the first team on a full-time basis after making a big impression on Solskjaer.
Luton possible starting lineup:
Shea; Bree, Lockyer, Bradley, Norrington-Davies; Shinnie, Moncur, Tunnicliffe; Clark, Hylton, LuaLua
Man United possible starting lineup:
Henderson; Wan-Bissaka, Bailly, Maguire, Williams; Matic, Fred; James, Van de Beek, Greenwood; Ighalo
We say: Luton 1-2 Man United
Luton will be full of confidence after making a strong start to the season, but we fancy United to book their spot in the next round of the competition. Both managers will make wholesale changes from their league encounters at the weekend, and the away team's superior quality should ultimately shine through.