Thomas Tuchel and company are still doing everything they can to try to secure a right-back/center-back hybrid player before the window closes as they are in need of bringing in defensive reinforcements of that profile.
Bayern is currently without the services of Kim Min-jae and Noussair Mazraoui due to international competitions and Tuchel has experienced a handful of defensive injuries this season as all of Dayot Upamecano, Matthijs de Ligt, and Alphonso Davies have all been injured at one point or another. More than once this season, Tuchel has had to use Leon Goretzka as a center-back due to having no one else available.
As far as defensive depth is concerned, youngster Frans Krätzig is still in the ranks for Bayern, but the club has remained open in potentially accepting a loan deal for the 21-year old that has showed glimpses of bright potential. So far this season, he has made a total of seven senior appearances for the club.
Per information from Belgian outlet DH les Sports (via @iMiaSanMia), Bayern has rejected a loan offer from Standard Liège this winter for Krätzig. The Belgian club reportedly wanted to have a buy-on clause in the loan deal to explore the potential of getting the defender on a permanent basis after the loan spell, but Bayern was not interested in allowing said clause to be attached to the deal. As a result, Bayern rejected the offer that was submitted.
For now, Krätzig is still a Bayern player, but that could change if the right offer comes in from the right club before the winter window closes. It could also depend on whether or not Bayern is able to secure a right back or center back as they have made very clear they are trying to do so. The club can ill afford to lose a defender without gaining one at this juncture.