The 21-year-old, with Jose Mourinho keen on resting players ahead of the Europa League final, was handed a chance to impress from the start on the left hand side.
And he enjoyed a dream start to his senior career, rifling home an unstoppable strike after swerving past the entire Palace back four before going on to impress with a number of powerful runs as the game went on.
According to M.E.N‘s Samuel Luckhurst, the youngster had been offered a new deal prior to impressing against Sam Allardyce’s men.
This has been something of a dream week for Harrop: a hat-trick against Tottenham Hotspur, a new deal on the table, and then, to top it all off, a goal on his debut – sheer footballing nirvana for any youngster who has spent years grafting in the youth ranks.
His contract was set to expire over the summer but the club, even before his rip-roaring senior debut, clearly felt he had a future at Old Trafford; his confident, effervescent display on Sunday would have only reinforced such a notion ahead of pre-season.