Sunderland have approached Aston Villa regarding a potential loan move for Tommy Elphick.
The Black Cats have been tracking the experienced defender all summer.
The 29-year-old, who signed for Villa last summer after playing a key part in Bournemouth's rise to the Premier League, has been told he is free to leave by Steve Bruce.
They would prefer a permanent deal, with Bruce saying last week his departure was merely a matter of a team 'hitting the number'.
Birmingham City have also been interested in the centre-back, but on Wednesday completed the signing of Harlee Dean from Brentford.
Sunderland are also monitoring the progress of Manchester City youngster Tosin Adarabioyo, according to the Daily Mail.
The Black Cats are pursuing loan deals due to financial restrictions, with Grayson also determined to bring in a striker before the window shuts at 11pm on Thursday.
EFL rules state that a club can only name 5 loanees in any matchday squad.
Sunderland already have three established first team players on loan in Tyias Browning, Brendan Galloway and Lewis Grabban.