Aaron Cresswell has extended his stay at West Ham by signing a new five-year contract.
Phil Jones has signed a new deal with Manchester United which keeps him at Old Trafford until June 2019.
Derby manager Nigel Clough is targeting six new signings this summer but has warned players must also leave Pride Park.
Clough has stepped up his search for new players with the season nearing its close and has already held talks with some of his targets.
He told the Derby Telegraph: "I think half a dozen signings is the target we have come up with and they are pretty much set in our mind.
"But there will be some going out. It will not be a case of just adding six to the squad. A few will be going, but hopefully not the important ones.
"The recruitment process has been stepped up since Saturday. We are talking to some players who we would like to bring in. We have started to talk to one or two who will be out of contract, and we are getting a positive response."
Striker Chris Martin and left-sided player Craig Forsyth, currently on loan with the Rams, are among Clough's targets.
Martin is out of contract at Norwich this summer and Forysth has another year to run on his deal at Watford.
On those two, Clough added: "They have done well for us and there is a possibility of them coming in.
"Chris is out of contract, so there will be more clubs after him. Craig has got a year left at Watford, so that will be dependent on their stance."