Matthaus saw plenty of the Dane when he was on-loan with Borussia Monchengladbach.
He wrote for The Sun: “I saw a lot of Danish defender Christensen when he was loaned out to Monchengladbach.
“At 21, he is the future of Chelsea. He is intelligent, he reads the game and gets into position.
“Monchengladbach had hoped to get him for another year — but I suspect Conte saw Christensen was ready to play for a big team.
“Another good thing for Chelsea is that Eden Hazard has hit form after breaking his ankle in the summer.
“He is improving all the time and working well with Alvaro Morata.
“Hazard has found his level again, dangerous whenever he gets the ball and scoring goals.
“That is what good players can do — and he is certainly a top player.”