Schalke 04 could be without forward Raul when they take on Cologne on Saturday after the Spaniard missed some training this week due to a stiff calf muscle, coach Huub Stevens said on Friday.
"We have to wait and see how it looks with Raul on Saturday," Stevens told reporters. "It is still unclear."
Schalke are in third place, jointly on 37 points with leaders Bayern Munich and Borussia Dortmund, while Raul has scored 10 league goals.
VfL Wolfsburg take on leaders Bayern Munich on Saturday with Alexander Madlung and new signing Vierinha doubtful with minor injuries.
Coach Felix Magath said on Friday that Jan Polak had already been ruled out with an injury picked up during the winter break and had broken off training in mid-week.
Magath, however, can count on his top scorer Mario Mandzukic, who missed the season's restart last week.
"He has trained well all week and if he remains as he is at the moment then he can expect to play," Magath told reporters.
Hertha Berlin have signed defender Felix Bastians from Freiburg on a deal to 2016, the club said.
"This is the best solution for everyone," said Hertha sports director Michael Preetz, who is looking to strengthen the team's back line.
Hertha, who host Hamburg SV on Saturday are in 13th place, three points off the drop zone.
