The fallout from Leeds signing Rob Green could see Bailey Peacock-Farrell as the big winner.
But the Sunderland boss could face competition from former Tottenham Hotspur manager Harry Redknapp.
Celtic beat Olimpija Ljubljana 2-1 on Wednesday evening.
Spurs are allegedly anticipating a bid from Hull City for midfielder Ryan Mason.
Birmingham have been linked with Kieran Richardson, who was relegated with Aston Villa last season.
Ibrox side Glasgow Rangers have signed Matt Crooks from Accrington Stanley.
The Premier League winners will meet the Scottish Premiership side later this month.
Newcastle United are still deciding over whether to loan out Adam Armstrong.
Sunderland are yet to make a signing in the summer transfer window.
Paulinho was sold by Tottenham Hotspur last summer.