Jordan Willis is the only senior centre back currently on the Black Cats’ books, with Tom Flanagan weighing-up a contract offer.
So who could Parkinson be targeting to add some depth to the ranks? Here, we take a look at some of the best centre backs who are currently available as free agents – with some attractive options:
1. Ben Heneghan
A familiar name to Sunderland fans having been linked with the club in the past, Heneghan has been released by Sheffield United having spent time on loan at Blackpool. Photo: Mark Runnacles
2. Jonathan Grounds
No stranger to the North East having spent time with Middlesbrough, the experienced Grounds is without a club after being released by Birmingham City. Photo: Steve Welsh
3. Bailey Wright
No surprises that Wright's name is on the list, and he's certain to be name that Sunderland are pursuing after he left Bristol City. Photo: Frank Reid
4. Donervon Daniels
With vast experience in League One, Daniels will no doubt be being pursued by a number of clubs this summer after his exit from Luton Town. Photo: Dan Mullan