Wirtz stretchered off as Leverkusen beaten in home derby by Cologne

Wirtz, 18, twisted his left knee in a first-half challenge and the attacking midfielder was taken to hospital after being carried off in clear distress. "That's very disappointing - I'm really sorry for him," Leverkusen defender Jonathan Tah told DAZN, as his club wait for Wirtz's diagnosis.

His injury makes Wirtz doubtful for Germany's friendlies at home to Israel on March 26 and the Netherlands away three days later. His injury capped a bad day for Leverkusen as Cologne's Kingsley Schindler came off the bench to volley in a superb second-half winner for his first Bundesliga goal.

The loss of Wirtz could be a serious blow to Leverkusen with their top-scoring Czech striker Patrik Schick already sidelined by a torn calf. Leverkusen remain third in Germany's top flight despite the defeat. They are 15 points behind league leaders Bayern Munich who were held to a 1-1 draw at Hoffenheim on Saturday.

This is Leverkusen's second straight defeat after losing to Atalanta in their Europa League last 16, first-leg tie on Thursday. Cologne are seventh in the table as Steffen Baumgart's visitors out-thought and out-muscled Leverkusen.

The hosts lost three players in the first half of a bruising derby. Leverkusen's Dutch defender Jeremie Frimpong had to be helped off with a leg injury after a crunching tackle before Wirtz left on a stretcher.  Leverkusen centre-back Odilon Kossounou also went off injured just before half-time.