Marco Reus faces a desperate wait to learn whether his Qatar 2022 World Cup ambitions are over after suffering suspected ankle ligament damage.
The Germany forward sustained the blow on Bundesliga duty with Borussia Dortmund in the derby against Schalke on Saturday, having to be stretchered off the pitch during the first half.
His pain was apparent, and with Germany's World Cup opener against Japan less than two months away, Reus may struggle to recover full fitness in time.
Dortmund head coach Edin Terzic said Reus felt "severe pain", while match-winner Youssoufa Moukoko said he would "hope and pray" his team-mate recovers soon.
"There is no one I talk to more often than our team doctor at the moment," Terzic said. "Today it hit our captain. It is extremely bitter, it was extremely unfortunate. Marco injured his ankle.
"I was only able to speak to him briefly at half-time. Then he was in severe pain. How badly the ligaments are injured, we can't answer yet. It's a shame because Marco was in excellent form, he was in great shape and played great."
Reus was named in Germany boss Hansi Flick's latest squad on Thursday ahead of Nations League games against Hungary and England.
Flick will be concerned by the prospect of losing the 33-year-old, who has won 48 international caps.
That would be particularly cruel for Reus, given he missed out on Germany's 2014 World Cup triumph after suffering an ankle injury in a warm-up game for that tournament. Another injury blow, to his groin, forced Reus out of Euro 2016.
"He has experienced so many setbacks in his career," said Terzic. "We had hoped that he would finally be through with it, especially now in the World Cup year. We hope it's not as serious as it looked."
Moukoko, the 17-year-old whose winner against Schalke made him the youngest Bundesliga scorer in the history of the Revierderby, dedicated his goal to Reus.
He told German broadcaster Sky Sport: "When Marco is on the pitch you feel better, you have the confidence, and I just hope and pray it's not that bad."