Bayer Leverkusen slumped to a 1-0 loss to visitors Cologne in their Rhine derby on Sunday and their Germany international Florian Wirtz suffered a torn knee ligament that will keep him out for months in a double blow to their bid to hold on to a top-four spot this season.
That completed a nightmare afternoon for the hosts with teenager Wirtz, who has contributed 10 assists -- the second most in the league this season -- as well as seven league goals, going down injured in the 27th minute.
Among the most talented German players of his generation, the 18-year-old, who has four senior caps for Germany, turned his left knee when his studs got stuck as he shifted direction with the ball.
He was taken to hospital with club later saying he would be out for several months after having torn the anterior cruciate ligament in his left knee.
Earlier, team mate Jeremie Frimpong had also been taken off, with what Leverkusen said was a likely ankle injury.
They could have levelled late in the game but Sardar Azmoun twice spectacularly miskicked in front of goal to waste their chances for an equaliser.