Borussia Dortmund are sweating on the fitness of key defender Mats Hummels for Tuesday's Bundesliga top-of-the-table showdown at home to leaders Bayern Munich.
The 2014 World Cup winner aggravated his Achilles tendon in Saturday's 2-0 win at Wolfsburg which kept second-placed Dortmund four points behind leaders Bayern, who are chasing an eighth straight league title.
Hummels was replaced at half time on Saturday but will be keen to to face his former club whom he spent three years with before transferring back to Dortmund in 2019.
"Mats has a problem with his Achilles tendon and we hope he can play on Tuesday," said Dortmund sports director Michael Zorc.
"He has had the problem for a while."
Hummels was treated at Dortmund's training ground on Sunday and if he is not fit, Emre Can, who replaced Hummels in Wolfsburg, will most likely deputise against Bayern.
Bayern coach Hansi Flick has fitness concenrs of his own with midfielder Thiago Alcantara and defender Jerome Boateng struggling with groin and muscle strains respectively.
Alcantara sat out Saturday's 5-2 thrashing of Eintracht Frankfurt in Munich while Boateng came off late in the second-half.
Bayern hammered Dortmund 4-0 at the Allianz Arena in Munich when the teams last met in November.
The Bundesliga became the first top European league to return during the coronavirus pandemic last weekend with all matches played behind closed doors.