Borussia Dortmund teenage star Konstantinos Karetsas was taken to hospital after slumping to the turf 25 minutes into his Champions League debut against Villarreal on Tuesday. The 18-year-old Greece prospect signaled distress to the referee after passing the ball, then sat on the grass before being treated and stretchered off. Dortmund confirmed he left due to circulatory problems and is doing well under the circumstances, undergoing further tests.

Goalkeeper Gregor Kobel expressed hope for his swift return. Karetsas, signed for €30 million from Genk, and Giannis Konstantelias, signed for €26m from PAOK, were Dortmund’s marquee summer additions. Konstantelias’ season is likely over after an ACL injury on his Bundesliga debut.

Dortmund won the match 3-2, with an own goal from Renato Veiga and a late brace from Serhou Guirassy on his 100th appearance. Information from the Associated Press contributed to this report.