The Red Devils starlet was shown a yellow card for simulation after throwing himself to the ground with the 30-year-old centre-half in close proximity.
The 18-year-old was warned by his manager David Moyes not to let diving "creep into his play" and Collins is confident the Belgian-born youngster will heed that advice.
However, the Wales international was nontheless unequivocal in his view of the incident with Januzaj.
"It's cheating, basically," Collins told Sky Sports News.
"I don't like to see it in the game. He probably thinks I am going to stick my leg out and he's probably already thinking about going over.
"Obviously he's taken a dive. He's a young lad, a great player, I'm sure he will learn.
"David Moyes seems to have this conversation quite a lot at his club with Ashley Young.
"It happens in football. He (Januzaj) is a great player and played very well at the weekend. He's learning the game and if he carries on playing the way he is, he is going to be a top-drawer player."