Timo Werner asked to leave the pitch half an hour into RB Leipzig's 2-0 Champions League defeat at Besiktas on Tuesday due to breathing complications.
Werner, 21, requested to be substituted 32 minutes into the game at the Vodafone Park after struggling with what Leipzig coach Ralph Hasenhuttl later described as "breathing and circulation problems."
The Germany international had earlier been handed ear plugs by the club's team doctor after only nine minutes, but amid an intense atmosphere in Istanbul, he continued to struggle and was seen throwing them away a few minutes later.
When Hasenhuttl wanted to withdraw Naby Keita, who had already been booked, Werner asked to leave the pitch instead, and the Leipzig boss later confirmed to reporters that the striker did not feel well.
"Timo no longer wanted to be on the pitch because of circulation and breathing problems," he said. "But he feels better again."
Werner, who has started in every match for Leipzig and Germany this season, is to undergo a medical check-up to determine whether exhaustion could be the cause of the problem, kicker reported.
In March, Keita collapsed following a home defeat to Wolfsburg and spent one night in hospital, though no further problems were discovered.
Hasenhuttl said his side had been surprised by the noise at Besiktas' Vodafone Park, and put a difficult first 45 minutes, in which they conceded two goals, down to their lack of experience at Champions League level.
"We lost against the atmosphere in the first half," Hasenhuttl said. "We could not handle it. That was definitely the main problem at the beginning. Such an atmosphere in our first away match was a bit too much for some of our players.
"It's a deafening noise. It provokes stress. How can you prepare the lads for it? It's not possible. It's an experience you need to make. It's hardly surprising it happens in our first Champions League season."
As Leipzig improved in the second half, the match was stopped for over 10 minutes when the floodlights went out, but Hasenhuttl refused to use that as an excuse for the defeat.
"While we were putting pressure on the opponent, the lights went out," Hasenhuttl said. "Evil be to him who evil thinks. It happened."