That’s according to former player turned pundit Ray Wilkins who’s slammed the Blues for selling the Serbian.
Matic swapped Stamford Bridge for Old Trafford in July and has impressed in a red shirt.
The 29-year-old was an important member of Antonio Conte’s title-winning team last season.
And Wilkins says Matic has improved Chelsea’s Premier League rivals and given Paul Pogba a new lease of life.
“It’s the worst [decision] I’ve ever seen, if I can say,” Wilkins said on Sky Sports.
“I cannot see that for the life of me.
“You’ve got a guy here who was so paramount to Chelsea along with Kante in the middle of the pitch, winning the championship with Chelsea the year before and all of a sudden you’ve sold him to one of or the biggest rival we have.
“I say we because I am a Chelsea supporter so I’m speaking from the heart when I speak.
“I just could not see that for the life of me, why would we let Nemanja go there?
“He’s been outstanding for us and you’ve seen in the short period that he’s been there how he’s allowed Pogba to basically do what he wants.
“I just couldn’t see that piece of business at all.”
Magic played 121 games for Chelsea and scored fours goals after being re-signed from Benfica in 2014.
