Manchester United finished in fifth place and won the FA Cup under Louis van Gaal last season.
Aged 16 years, 263 days, Angel Gomes became the club's youngest ever player in the Premier League when he came on as a late substitute for Wayne Rooney.
The Red Devils are focusing on the Europa League final, knowing beating Ajax in the final will mean a ticket to the Champions League.
MANCHESTER UNITED: Pereira 6, Jones 7, Bailly 7, Fosu-Mensah 7, MITCHELL 8, Tuanzebe 7, McTominay 7, Pogba 8 (Carrick 88, 6), Lingard 6 (Martial 47, 6), Rooney 7 (Gomes 88, 6), Harrop 8.
Harrop still had work to do, as he entered the Palace area, but beat defender Martin Kelly easily and cut into a central position before placing a powerful shot into the far corner.
Given the millions in prize money up for grabs that was little surprise, yet the way the hosts' callow side bossed much of the game did.
The France worldwide pointed to the skies after his goal - presumably in honour of his father who passed away earlier this month. If so United's record goal-scorer and longest-serving player, having joined in August 2004, would leave with no chance of saying goodbye to the home crowd.
And it was two for United within four minutes, a fast counterattack capped when Lingard's pass found its way to Pogba after a mistake from Joel Ward, allowing the France worldwide to fire a low left-footed finish beyond Hennessey.
Jose Mourinho is adamant that Manchester United's academy players aren't ready to face Crystal Palace on Sunday, but says he has been left with no other choice.
"Obviously there is a big difference of quality, strength, experience between them and good players, experienced players like Crystal Palace have".
When they preserved their Premier League status with last Sunday's 4-0 defeat of Hull he also said he does not want to be fighting relegation again in 12 months' time, but he has added: "Can we challenge for Europe?"
The Eagles have never won at Old Trafford in the Premier League and despite the team sheets, might not find it so easy.