Black Cats Sporting Director Kristjaan Speakman has said the club are unlikely to look at the free agent market after missing out on a couple of deals on deadline day.
Still, there are gaps in the Sunderland squad that could be addressed following injury setbacks in some areas.
Ross Stewart and Dennis Cirkin both appear to have suffered lengthy injury setbacks, while defender Danial Ballard will be sidelined for the next few months with a fractured foot.
There are also a lack of options to replace captain Corry Evans in the holding midfield role.
Here are nine free agents that Championship clubs could still sign.
1. Massimo Luongo (centre midfield)
After missing out on promotion from League One with Sheffield Wednesday, the combative midfielder, 29, turned down a new contract at Hillsborough. He has made 193 appearances in the Championship for QPR and The Owls. Photo: Stu Forster
2. Michael Hector (centre-back)
Another player with lots of Championship experience following spells at Reading Sheffield Wednesday and Hull. The right-footed centre-back, 30, made just four second-tier appearances for Fulham last season and left after two and a half years at the club. Photo: Catherine Ivill
3. Neil Taylor (left-back)
A player who was also a free agent last summer, but proved a solid signing for Middlesbrough after joining the club in November. The 33-year-old made 17 appearances in all competitions, operating in a left wing-back role. Photo: Stu Forster
4. Ryan Bennett (centre-back)
While he's predominantly played as a right-sided centre-back, Bennett has also played across a back three at former clubs Wolves and Leicester. The 32-year-old made 18 Championship appearances last season before being released by Swansea. Photo: Stu Forster