Phil Parkinson is keen to add at least one more defender to his ranks before the October 16 deadlines, and that number could increase after an injury to Arbenit Xhemajli on international duty.
So who could be available in the free agent market? Scroll down and click through the pages as we take a look at the players Sunderland could consider:
5. Stephen Kingsley
Kingsley left Hull City this summer with the aims of securing a Championship move, but League One may prove an option as we enter the final stages of the window. He can play both as a centre back and left-back, which may prove enticing to Sunderland. Photo: Lynne Cameron
6. Jack Hobbs
Well-known to Phil Parkinson, whom he worked under at Bolton Wanderers, the experienced Hobbs is currently without a club. He could prove a good short-term fix if Sunderland urgently need some cover at the back. Photo: Harry Trump
7. Joel Lynch
This may not be the most popular of suggestions, but Lynch is still available after his summer exit from the Stadium of Light. Stranger things have happened... Photo: George Wood
8. Ryan Shotton
While traditionally a full-back, Shotton - who was released by Middlesbrough - could deputise at centre back. His wages could be an issue though, particularly under the League One salary cap. Photo: Nathan Stirk