The 21-year-old picked up the Player of the Year award at Pride Park last year after an excellent campaign in the play-offs, which resulted in the Rams losing in the play-off final to Aston Villa.
Having worked with him last year, Lampard has said he can trust the centre-back who is now his preferred option at the back.
Speaking in his press conference, Lampard said: "I worked with him last year. I had a lot of trust with him.
"I wanted to keep him and not loan him into the Premier League where he was wanted by many clubs."
But as fellow defender Antonio Rudiger is set to return from a groin injury, Lampard insists that the German won't walk back into the side and replace Fikayo Tomori.
"I don't see it as one for one with Rudiger [for places]," Lampard said in France.
Antonio Rudiger is ruled out of tomorrow's game against LOSC Lille so Fikayo Tomori is set to be joined by Andreas Christensen at the heart of the Blues' defence at the Stade Pierre Mauroy.