In the meantime, here's every signing the Black Cats have made in January over the last decade, and a look at where they are now.
17. Grant Leadbitter - January 2019
Back at his boyhood club a decade later, the midfielder is one of Phil Parkinson's key players. (Photo by Charlie Crowhurst/Getty Images) Photo: Charlie Crowhurst
18. Will Grigg - January 2019
The Northern Ireland international has been unable to recapture his goalscoring form for Sunderland, after a season and a half at the club. (Photo by Alex Davidson/Getty Images) Photo: Alex Davidson