The 18-year-old midfielder is now one of the most talked about players in the Premier League after his stunning brace on his full league debut at the weekend in the win over Sunderland.
But Anderlecht are left thinking what might have been, having sold him to United just two years ago.
"Today we are big losers," admitted Anderlecht academy director Jean Kindermans to Sky Sports News.
"Adnan was a nice player and technically, very very skilled, very intelligent on the pitch - a hard worker, but a silent worker."
Kindermans admits that Januzaj has not changed, even now he is in the first-team at Old Trafford.
"There are 12, 13, 14-years-olds who have earrings and special hair, but Adnan was a nice quiet boy and when I see him now playing for Man United, he has not changed."
Kindermans insists that Anderlecht were helpless to prevent Januzaj leaving once United made their move.
"If the father decides the son is leaving us, then we have to make the best deal possible," he said.
"Three years ago we thought it was a good deal, today we have to say it was a good deal but it isn't anymore!"