Chelsea legend Ray Wilkins has described the club's decision to sell Nemanja Matic to Manchester United as "the worst" they have made in a long time.
The Serbian midfielder made the switch to Old Trafford for £40million in July and has wasted little time in becoming an integral member of Jose Mourinho's Premier League leaders.
Wilkins, who enjoyed both playing and coaching roles at Stamford Bridge, has been left bemused by his former employer's decision, and believes it has given United a significant edge in this season's title race.
"It's the worst decision I've ever seen," Wilkins told Sky Sports. "You've got a guy here who was paramount to Chelsea along with Kante in the middle of the pitch, winning the title with Chelsea the year before, and all of a sudden you've sold him to one of - or the biggest - rivals 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 [at Man Utd] how he's allowed [Paul] Pogba to basically do what he wants. I just couldn't see that piece of business at all."
