The throwback video, taken during the FA Cup semi-final at Villa Park in 2004, shows the England midfielder scythe down a 20-year-old Reyes with a horror tackle.
Launching himself at the Spaniard from behind, Scholes snaps through Reyes, bending his trailing leg at a horrific angle to leave him prone on the ground.
Mystifyingly, the challenge was deemed worthy of only a yellow card by referee Graham Barber.
It left substitute Reyes with minor medial ligament damage, keeping him out of action for around three weeks.
But after a clip of the tackle resurfaced on social media site Reddit this week, United fans agreed it could have been a career-ender.
“That’s an outrageous tackle. Nothing to be proud of in my opinion,” one supporter wrote.
Another said: “Personally I never really liked this part of his game.
“He clearly did this on purpose and could have broken Reyes’ leg.
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“There’s physical play and then there’s dangerous and excessive play. Disguising dangerous tackles as innocent mistakes is a bit dishonourable.”
“Paul Scholes was and still is my all time favourite player but the one downside to a model player was his habit of nasty tackles,” a third added.
Scholes retired in 2013 having spent his entire career at Old Trafford, being hailed as one of the finest midfielders of his generation in world football.
He currently works as a pundit for BT Sports.