Derby have signed Chelsea defender Fikayo Tomori on a season-long loan.
Tomori, 20, becomes the second Chelsea player to join Frank Lampard's Rams on loan, after Mason Mount's move earlier this summer.
He has previously been loaned out to Hull and Brighton, helping the latter win promotion to the top flight.
"He fits the profile for us; he is a talented young player and he already has experience in the Championship," Lampard told Derby's website.
"I know him from my connections at Chelsea and, like with the other players we have brought in on loan this summer, I am confident we can be good for them and they can be good for us."
Meanwhile, teenage winger Luke Thomas has signed a new four-year deal with the Championship club until the summer of 2022.
The 19-year-old has made two first-team appearances for the Rams and was among the substitutes for Friday's league win at Reading. He was named as Derby's Young Player of the Year last season.
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