Juan Mata, Marcus Rashford and Mason Greenwood were all on target, though Dean Henderson made a vital contribution on his debut.
Dean Henderson strengthened his case to be Manchester United's number one with a brilliant save late on as Ole Gunnar Solskjaer's disjointed side beat Luton Town 3-0 in the EFL Cup.
United suffered a 3-1 home loss to Crystal Palace in their first Premier League game on Saturday and Solskjaer made 10 changes for the third-round tie at Kenilworth Road, including handing a debut to goalkeeper Henderson as David de Gea was given the night off.
A Juan Mata penalty on the stroke of half-time gave United the lead against their Championship hosts, who would have levelled with nine minutes remaining had Henderson's one-handed stop not denied Tom Lockyer.
By that point a concerned Solskjaer had called for the cavalry and substitutes Marcus Rashford and Mason Greenwood both added late goals for a margin of victory that flattered United.
Harry Maguire was the only United player retained from those who started the defeat to Palace, though the newcomers looked just as rusty as those they had replaced.
On one of the few moments United's attack clicked, James Shea saved from Mata after Donny van de Beek stepped over Jesse Lingard's pullback.
Luton, who hit the side netting through Danny Hylton, looked like entering the break on level terms but George Moncur's clumsy barge on Brandon Williams resulted in a 44th-minute penalty that Mata tucked away.
There was little improvement from the visitors after the break, though Lingard did have an effort cleared off the line by Ryan Tunnicliffe, while Shea was equal to attempts from Nemanja Matic and Van de Beek.
Solskjaer brought on attackers Bruno Fernandes, Rashford and Greenwood with 11 minutes to go, though the next goal very nearly came at the other end, with Henderson springing to his right to push out Lockyer's header before Eric Bailly blocked the follow-up attempt.
Rashford collected Greenwood's pass and slotted home to kill off any Luton hopes with two minutes remaining, the teenager then opening his account for the campaign with United's third in stoppage time.
What does it mean? Job done but little to enthuse Solskjaer about squad depth
Solskjaer was reliant on the same XI towards the end of last season and the understudies' display here perhaps showed why.
It was telling that he felt he needed to bring on Fernandes, Rashford and Greenwood to make sure of the victory. It was a further indication that strength in depth is not a luxury the United boss has, except for between the sticks…
Henderson makes his mark
Henderson, who spent 2019-20 on loan with Sheffield United, has returned to Old Trafford to challenge first-choice keeper De Gea after the Spaniard made some high-profile errors last term.
Luton did not have a shot on target until Lockyer's two late attempts and Henderson showed brilliant anticipation to fling himself to his right and claw away his initial header.
Ighalo fails to inspire
The Nigerian proved a useful alternative in cup competitions in 2019-20 - scoring five times across the Europa League and FA Cup - but he dallied with the only chance that came his way in the second half and saw it blocked.
Even though they were on the pitch for just 11 minutes, both Rashford and Greenwood had two shots apiece and scored.
Key Opta facts
- Solskjaer has won 50 of his 92 games in charge of Manchester United across all competitions – only Ernest Mangnall (78 games) and Jose Mourinho (81 games) have reached 50 managerial wins in fewer matches for the Red Devils.- Since the start of last season, United have both taken (23) and scored (19) more penalties in all competitions than any other English league side.- Rashford has been involved in 10 goals in his past seven EFL Cup appearances, with seven goals and three assists.- Greenwood was the first United substitute to score and assist in this competition since Rashford in September 2016 against Northampton, with both players aged 18 at the time of achieving this feat.
Solskjaer's side return to Premier League action at Brighton and Hove Albion on Saturday, the same day Luton visit rivals Watford in the Championship.
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