Borussia Dortmund teenager Konstantinos Karetsas was forced off on a stretcher and taken to hospital after suffering circulatory problems during his Champions League debut against Villarreal on Tuesday.

The 18-year-old Greece prospect was involved in the action around the 25-minute mark when he passed the ball to a teammate before signalling to the referee that he was in distress. Karetsas then sat down on the pitch as medical staff rushed to attend to him.

ALSO READ: Real Madrid 2-1 Inter Milan: Mourinho’s Tactical Masterclass Guides Los Blancos To A Hard-Fought UCL Win

Karetsas Receives Treatment

The youngster was treated while lying on the pitch before being placed on a stretcher and carried off for further medical assessment.

“Konstantinos Karetsas had to leave the field due to circulatory problems,” Dortmund said in a statement. “Kosta is doing well under the circumstances and is on his way to the hospital for further tests.”

The incident caused concern among the players and supporters, with Karetsas' health taking priority as he was taken away for further examination.

Kobel Sends Message To Karetsas

Dortmund goalkeeper Gregor Kobel expressed his hope that the teenager's condition was not serious and that he would be able to return soon.

“I hope and I think that everything is OK and I hope that he's back and fit with us soon,” Kobel told broadcaster Amazon Prime.

Further tests at the hospital will determine the extent of Karetsas' issue.

Dortmund Beat Villarreal 3-2

Karetsas' Champions League debut ended prematurely, but Dortmund eventually secured a 3-2 victory over Villarreal.

The match was still goalless when the teenager left the field. Dortmund will now await further updates on his condition following the worrying incident.

ALSO READ: WATCH: Mbappe Levels Raul’s Record, Finds The Net Against Inter As Forward Responds to Critics

Karetsas Joined Dortmund For €30 Million

Karetsas was one of Dortmund's major summer signings, arriving from Genk for a reported €30 million. The former Belgium youth international has been regarded as one of Europe's promising young talents.

His Greece teammate Giannis Konstantelias also joined Dortmund during the offseason for around €26 million from PAOK. However, Konstantelias suffered an ACL injury on his Bundesliga debut last month and is expected to miss the remainder of the season.

Dortmund will now hope Karetsas' latest setback is not serious and that the teenager can return to action soon.