Having secured the services of David McGoldrick earlier this month, boss Chris Wilder has revealed talks are ongoing with three other key players about new contracts.
Speaking after Saturday's deserved point at promotion rivals Norwich City, the Blades boss remarked: "David fully deserved it, he came on a short-term deal and he's earnt the lift.
"There are talks going on with Billy, Enda and Jack too, they all deserve to be rewarded."
Wilder added: "I'm trying to kick us on within reason, but there was some interest in David and I'm not surprised given his form this season.
"I'd love them all to stop and I'd imagine the boys would want to, their careers have progressed with us."