Ireland defender John Egan has committed his future to Sheffield United with a contract extension which keeps him at Bramall Lane until 2024.
But Shane Duffy's exit from Brighton moved closer after the Seagulls agreed a new deal with defender Lewis Dunk, who had been linked with a move to Chelsea.
Blades boss Chris Wilder says the club took the decision to offer Egan that security as payback for the work he has put in.
"We've got to reward and secure our best players and John is certainly one of those, we have to thank the board for their support in allowing us to put this deal together," Wilder said.
"John has been outstanding and knowing the boy as we do, we know John is not a comfortable footballer, he wants to establish himself and continue to improve at the highest level."
Egan joined the Blades from Brentford in 2018 and he was happy to stay on. "The last two years have probably been the most successful of my career and to get the chance to sign a new contract here is brilliant for me and I'm really looking forward to the future. I need to thank everyone involved," Egan said.
"I've loved my time here. We won promotion in the first year and had a real good first season back in the Premier League, so now it is about building on that and improving."
Meanwhile, Irish defender Warren O'Hora has left Brighton to join MK Dons on a season-long loan.