Tiago has been a transfer target all summer, but Chelsea were thought to be stalling on a deal because of his asking price. But according to Peter Kenyon, this has all been ironed out.
Kenyon told a Portugese newspaper: "The deal is practically complete.
"Benfica have given their permission for the player to come to London and on Monday he will have a medical.
"If everything goes to plan, Tiago will be officially presented as a Chelsea player on Tuesday."
The fee is thought to be between £7-10 million.