Bardsley, 22 who is currently on loan at Bramall Lane has been deemed surplus to requirements by Sir Alex Ferguson at Old Trafford and was placed on the transfer window last summer - but has been closely monitored by Sunderland recently; and after their 7-1 drumming at Everton is quite clear there back four needs strengthening.
"Bryan Robson and I are pursuing enquiries for both players with both parent clubs," said Blades football chairman Terry Robinson, who hopes to land the pair on permanent deals.
"One seems quite positive, while the other is keeping its options open."
In-demand Bardsley hinted that the prospect of first-team football was crucial: "I want to be playing at this stage of my career. My future is in my hands, but of course other people will also have a say in it."