Mason Greenwood scored twice as a second-half Manchester United blitz secured a 4-0 victory over AZ Alkmaar at Old Trafford and top spot in Europa League Group L.
United were well off the pace in the first half but came alive in the second as four goals in a devastating 11-minute spell blew AZ away.
Ashley Young's superb finish from an acute angle kicked United into gear after the interval, and within five minutes the lead was doubled thanks to Greenwood's instinctive low finish.
With the floodgates well and truly open, United plundered more goals as Juan Mata drilled home a penalty and Greenwood doubled his tally with a clinical near-post drive.
Man Utd: Romero (7), Young (7), Tuanzebe (7), Maguire (7), Williams (7), Matic (6), Garner (6), Mata (7), Pereira (6), Greenwood (8), Martial (6).
Subs: Laird (5), Chong (6).
AZ Alkmaar: Bizot (6), Svensson (6), Clasie (5), Wuytens (5), Wijndal (5), Midtsjo (5), Stengs (6), Koopmeiners (5), Sugawara (5), De Wit (5), Idrissi (7).
Subs: Vlaar (5), Ouwejan (5), Druijf (5).
Man of the Match: Mason Greenwood
United's fourth group-stage victory sees them progress as group winners ahead of runners-up AZ, and ensures Ole Gunnar Solskjaer's side will be seeded in Monday's round-of-32 draw.
Who can Man Utd draw?
APOEL, Bayer Leverkusen, CFR Cluj, Club Brugge, FC Copenhagen, Eintracht Frankfurt, Getafe, Ludogorets, Olympiakos, Rangers, Roma, Shakhtar Donetsk, Sporting Lisbon, Wolfsburg.
How United blew AZ away
With their passage to the knockout stage already secure, Solskjaer challenged his United players to maintain the desire and level of performance that secured consecutive victories over Tottenham and Manchester City.
But after making nine changes, United were flat and rode their luck against a hungrier AZ side as Yukinari Sugawara and the lively Oussama Idrissi tested Sergio Romero in the opening 10 minutes.
Nemanja Matic returned from injury to make his first appearance in two months as United made nine changes following their Manchester derby victory. Harry Maguire and Anthony Martial were on the only players to retain their places as youngsters Mason Greenwood, Brandon Williams and James Garner returned to the starting line-up.
It took the best part of half an hour for United to wake from slumber, Greenwood stretched the AZ defence and cushioned a header into the path of Mata, but he blazed wildly over the target.
Mata saw a shot blocked and Harry Maguire saw a header saved on the line as United improved as the break approached, but the first half belonged to AZ, who should have taken the lead when Dani de Wit blazed over on 41 minutes.
Solskjaer got into his players at the break and it took just eight minutes to bear fruit, with Young finishing off a fine team move with a pinpoint finish after a fine team move.
United doubled their advantage five minutes later when Greenwood swept the ball home from 20 yards, and the 18-year-old won a penalty after Jordy Clasie bundled him to ground in the box.
Mata rifled United's third in from the spot on 62 minutes before Greenwood had the final word on an enthralling second-half performance with a low left-footed effort from the right side of the box.
Analysis: Greenwood brings feel-good factor
Sky Sports News reporter James Cooper…
'The feel good factor continues at Old Trafford with a ruthless second half performance that rewarded those who had stayed to watch after a tepid and forgettable first period.
'United were much changed but the experience they retained in the shape of players such as Mata, Matic and Young showed how much Solskjaer wanted top spot in the Group.
'But the show was stolen by Greenwood, his two goals dispatched fearlessly, taking him to four in the last five Europa League matches. That the spotlight shone so brightly on the 18 year old was a bit harsh on skipper Young, whose searing finish set United on their way.
'It's now three wins in a row for the second time this season and perhaps, as crucially, a clean sheet too, with youngsters Ethan Laird and Tahith Chong entering the fray once the points were sealed.
'Solskjaer rested many of his big guns ahead of Sunday's visit of Everton, a match that will provide real evidence of whether or not Manchester United are heading in a new direction.'
What the managers said…
Man Utd boss Ole Gunnar Solskjaer: "I've seen a few good young players. I played with Wayne Rooney, but in terms of natural finishing, Mason is one of the best I've seen. He was class. Mason is a natural footballer but the closer he gets to goal, the more dangerous he is. Right foot, left foot, a nightmare for defenders. All he needs to do is develop his heading and then he can be a proper striker."
AZ boss Arne Slot: "It's an understatement to say that we had a bad period in the second half, but maybe it shows the class of our opponents. The most important lesson is that it's all very well to play attractive football but you can still lose a match within a couple of minutes."
Stats: Glorious Greenwood
- Only Marcus Rashford (13) has scored more goals than Mason Greenwood (6) in all competitions for Manchester United this season.
- Mason Greenwood is the youngest player to score a brace in major European competition for Manchester United, aged 18 years and 72 days.
- Manchester United's 4-0 win over AZ Alkmaar was their biggest margin of victory in European competition since beating Feyenoord 4-0 in November 2016.
Live Renault Super Sunday
United host Everton at 2pm on Super Sunday - live on Sky Sports Premier League from 1pm - and AZ host Ajax in a top-of-the-table Eredivisie clash at 3.45pm, before both clubs learn their Europa League fate in Monday's round-of-32 draw.