The January transfer window is a notoriously difficult market for teams to navigate with clubs often reluctant to see their players leave midway through the season.
This usually means buying sides have to pay over the odds to land a player that could transform their fortunes on the pitch.
The free agent market offers clubs an opportunity to strengthen their squad without having to negotiate transfer fees with unwilling sellers.
And this is a market that Sunderland and their Championship rivals could exploit throughout the month as a way to strengthen their respective squads - but just who is available to sign on a free transfer?
Here, we take a look at 19 free agents that Sunderland could sign in January.
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1. Alejandro Pozuelo
Pozuelo last played for Inter Miami in the MLS before leaving the club when his contract expired at the beginning of the month. The Spaniard made 36 appearances for Swansea City during the 2013/14 season. Photo: Lauren Sopourn
2. Juan Fernando Quintero
Quintero has been capped 32 times by Colombia and has played in a variety of countries including Italy, France, China and Argentina during his professional career. Aged 29, he is still in his prime but finds himself as a free agent after being released by Shezhen FC in China. Photo: Rodrigo Valle
3. Salomon Rondon
The former West Brom, Newcastle United and Everton striker left the Toffees at the beginning of the month following an 18-month stint at Goodison Park. Rondon has shown an ability to score goals wherever he has been, although at 33, he may be past his best. Photo: Michael Regan
4. Cristian Tello
Tello burst onto the scene with Barcelona but couldn’t solidify himself a starting spot at the Camp Nou and had numerous loan spells away from the club. Tello joined Real Betis on a permanent basis in 2017 before moving to LAFC in August 2022. He is now a free agent after leaving the MLS side earlier this month. Photo: CRISTINA QUICLER