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Borussia Dortmund has revealed that 18-year-old midfielder Konstantinos Karetsas is back in team training after suffering medical issues during his Champions League debut. The incident occurred during Dortmund's 3-2 win over Villarreal on September 8, when Karetsas collapsed on the field and was subsequently stretchered off with suspected circulatory problems. He was taken to a hospital and remained there for much of the following week.

Dortmund confirmed that Karetsas is now participating in training sessions, having begun individual sessions earlier in the week and finally joining his teammates. However, the club has not disclosed the specific diagnosis for Karetsas, and it remains unclear whether he will be fit to play in the upcoming Bundesliga match against Stuttgart on Saturday.

Born in Belgium, Karetsas has represented Greece in international competitions. Local media have speculated that dehydration may have been a contributing factor to his medical emergency. Karetsas himself expressed optimism during a video recorded during a recent visit to his former club Genk, stating that all tests had returned negative and that he only needed to adjust to the intensity of the game.

Dortmund's sporting director Ole Buch noted that Karetsas had difficulty communicating while being taken off the field, as he was unable to speak at that moment. However, it is important to note that there were no prior warning signs of any circulatory issues preceding the incident.