Former Chelsea defender Mario Melchiot believes the Blues are making a terrible mistake in letting Nemanja Matic join rivals Manchester United.
The 28-year-old is expected to move to Old Trafford to again work under manager Jose Mourinho.
But the Dutchman has warned his former club to replace him with an equally-strong midfielder if they really decide to sell him.
"He was very crucial in some games Chelsea played last season and I think he did extremely well, even if he wasn’t starting every game," Melchiot told the Alan Brazil Sports Breakfast.
"There was a good balance in the midfield, sometimes with him or Fabregas next to Kante.
"You don’t want to make your rivals stronger, especially in the midfield where Jose Mourinho is always focused on having a strong midfield.
"If he [Conte] makes the choice to let him go to Man United, he better have good backing because, if not, it might come back and bite you later."
