Former Manchester United defender Gary Neville believes the person at Chelsea who is responsible for selling Nemanja Matic should be sacked.
The Blues have struggled to keep up with Manchester City and Manchester United in the Premier League this season, and suffered a devastating 3-0 defeat to Roma in the Champions League on Tuesday.
When asked what is going wrong at the defending Premier League champions, Neville stated that the decision to sell Matic to United was the main catalyst for their dip in form.
"What's gone wrong for Chelsea? One word. Matic," Neville told BBC 5Live.
"It's as simple as that. The minute they sold Nemanja Matic was a mistake.
"When you had Matic sat in front of you, alongside [N'Golo] Kante, there was protection. Whoever made that decision needs sacking. That is one of the poorest decisions I have ever seen in the Premier League.
"If you ask any of those Chelsea players who they would want back, they would say Matic. Chelsea replaced him with someone who is going to do the same job – [Tiemoue] Bakayoko is not that player, he is not a holding midfield player.
"They didn't replace Matic. I wouldn't have let him out of the building, I would have chained him to the training ground walls."