Black Cats boss Mick McCarthy is understood to be very interested in the 22-year-old Rotherham-born Richardson who has featured 41 times for Leeds this season, but has been unable to dislodge Gary Kelly in his favoured right-back role, spending much of the time in midfield.
Lennon has also been linked with a move to Tottenham but the Londoners have yet to cement their interest by making a firm bid.
Lennon has also been linked with a move to Tottenham but the Londoners have yet to cement their interest by making a firm bid.