Last season, Black Cats boss Alex Neil had to adapt by playing people out of position and switching to a wing-back system to accommodate an unbalanced squad.
Neil often set his sides up in a 4-2-3-1 formation at former clubs Norwich and Preston, and may want to deploy a similar system at Sunderland for the 2022/23 campaign.
While Sporting Director Kristjaan Speakman has said the Black Cats will have a competitive budget this summer, they will also be looking at the loan and free agent markets.
Here are nine players they could try to sign:
1. Neil Taylor
Dennis Cirkin was Sunderland's only recognised left-back for much of the 2021/22 campaign and it's an area the Black Cats will need to strengthen. Taylor, 33, was a reliable option for Middlesbrough last season, making 14 league appearances after joining the club in December. The former Swansea man is now a free agent.
Photo: Stu Forster
2. Andrew Hughes
Neil was in charge of Preston when they signed Hughes from Peterborough in 2018. While the 30-year-old has two years left on his contract at Deepdale, he would provide a reliable option at left-back, while he can also play in the heart of defence.
Photo: Charlotte Tattersall
3. Moses Odubajo
Sunderland also need more cover at right-back, even if Carl Winchester continues to play in defence. Odubajo is set to leave QPR this summer after making 28 Championship appearances during the 2021/22 campaign. The 28-year-old predominantly played as a right-back during his career but has also operated further forward and on the left.
Photo: Dan Mullan
4. Lee Buchanan
Derby managed to trigger a clause to extend the 21-year-old's contract by an extra year following reports they could lose him on a free transfer this summer. Still, The Rams' relegation to League One means there is likely to be increased interest in the highly-rated left-back.
Photo: Alex Livesey