Here, we look at the potential ins and outs at Bramall Lane.
1. Ravel Morrison
The former Manchester United man is expected to drop into the Championship to sign for Middlesbrough Photo: Marc Atkins
2. Panagiotis Retsos
Greece defender Retsos is close to joining United on loan until the end of the season (Photo credit: INA FASSBENDER/AFP via Getty Images) Photo: INA FASSBENDER
3. Leon Clarke
Clarke is free to leave the Lane, with Chris Wilder surprised no club has already come in for him Photo: Robin Parker
4. Richairo Zivkovic
The speedy striker is also expected to be unveiled before tonight's deadline Photo: Dean Mouhtaropoulos