Blind - a £14 million recruit from Eredivisie champions Ajax in September - was taken aback by the physicality of November's first meeting with Manchester City, which the Premier League champions won 1-0 at the Etihad Stadium.
Fast forward six months and Blind has become an integral member of United's midfield after adapting to life in England's top flight.
And the 25-year-old is braced for a ferocious battle on Sunday, with third-placed United looking to extend their lead over City.
"The biggest memory of that first Manchester derby was when I saw one of our players on the ball in the middle of the pitch when suddenly a City player came flying in," Blind told The Mirror.
"He was off the ground and his leg was straight and it was only because my team-mate jumped out of the way that he was not injured severely.
"I was stood right next to the tackle. I turned to the referee and screamed, 'Hey, this is crazy'.
"But the referee didn’t even blink. It was then that I realised what this derby is about and what English football is about.
"Tackles like that are allowed here and so you have to play in the same style. Now, just a few months later, it is automatic for me to tackle like that. I don't even think about getting stuck in with a straight leg."
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