The Stoke City loanee has been dropped to the reserves.
The German defender moved to the Bundesliga side in the summer in a surprise move, considering his relative success at the Britannia Stadium.
He signed with the hope of a permanent deal at the Volkswagen Arena – but the deal looks unlikely to go through at present.
Stoke's Philipp Wollscheid and West Ham's Michail Antonio in action
He has fallen out with the club’s manager Valerien Ismael and been dropped to play with the reserves, as reported by Sky Sports.
In January, he can end his loan spell in Germany and return to Stoke City, who are clearly prepared to play without him.
Sunderland could certainly benefit from another defensive recruit to help them in their battle for survival this season.
Preston's Jermaine Beckford in action with Stoke's Philipp Wollscheid
Wollscheid, who played 39 times for the Potters last season, is clearly a player who knows what it takes to thrive in the Premier League and could form a strong relationship at the back with Sunderland’s current defensive line-up with Lamine Kone.
If Wollscheid becomes available, then Sunderland should see if he fancies swapping the red-and-white stripes of the Britannia for the Stadium of Light.