Dennis Cirkin, Niall Huggins and Denver Hume are all expected to be sidelined until the new year, leaving Black Cats boss Lee Johnson with a big dilemma.
The Sunderland boss deployed Luke O’Nien at left-back during the weekend’s 2-0 win over Ipswich, while Carl Winchester has been moved to right-back this campaign.
Still, Johnson has a concerning lack of options in that area with games starting to come thick and fast ahead of the winter months.
Johnson has admitted he could be forced to change his side’s formation to accommodate his lack of senior full-backs, while Sunderland could also explore the free agent market.
The Black Cats won’t be able to sign players from other clubs until January but could bring in players who aren’t under contract.
Here are nine players they could look at.
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. Andre Wisdom
The Liverpool academy graduate made 38 Championship appearances for Derby last season and was reportedly in talks with the Rams over a new deal. Nothing was forthcoming, though, and the 28-year-old right-back has been a free agent since the summer. Photo: Alex Pantling

9. Cuco Martina
The Dutchman has kept himself in shape after leaving Everton last year. Martina, now 32, predominantly played as a right-back during his time at Goodison Park and also had spells at Southampton and Stoke. Photo: Michael Regan