Borussia Dortmund’s Champions League victory over Villarreal was overshadowed by a worrying moment involving teenage midfielder Konstantinos Karetsas. The 18-year-old was forced to leave the field after experiencing circulatory problems during his European debut. Karetsas received medical attention on the pitch before being taken to hospital for further examinations. Dortmund later confirmed that the youngster was stable under the circumstances. Konstantinos Karetsas Collapses During Dortmund vs Villarreal Karetsas was involved in the match before suddenly appearing to feel unwell around the 25-minute mark.