Dortmund's Konstantinos Karetsas Returns to Training Following Champions League Medical Scare

When an 18-year-old collapses off the ball on the biggest stage in European football, the sport stops. But just eight days after a terrifying Champions League debut, Borussia Dortmund's €30 million prodigy Konstantinos Karetsas is back on the grass.[2][7][8]

The Greek international resumed full team training on Wednesday, September 16, 2026, following a battery of hospital tests that cleared him of any underlying cardiac issues. It marks a massive sigh of relief for a club that feared the absolute worst.[2][7]

The scare unfolded 25 minutes into Dortmund’s 3-2 victory over Villarreal on September 8. After playing a routine pass, Karetsas signaled distress to the referee, slumped to the turf in tears, and was stretchered off the pitch.[1][3]

Dortmund’s medical staff quickly diagnosed the episode as acute circulatory problems, while local reports in his native Belgium pointed to severe dehydration. He spent the majority of the following week under observation in a local hospital.[1][2][5]

The panic on the touchline was palpable. Sporting director Ole Book admitted the severity of the situation as he accompanied the teenager off the pitch, stating, "I went out with him but in that moment, he wasn't able to speak."[2][5]

Yet the recovery has been as swift as the collapse was sudden. "I'm doing really well," Karetsas confirmed in a video posted to X on Monday. "We tested everything and everything is fine. I just need to adjust a bit to the intensity, but that will come with time."[2][7]

The relief in the dressing room is absolute. Goalkeeper Gregor Kobel had voiced the squad's immediate anxiety post-match, and managing director Lars Ricken praised the players' composure, noting, "It's not easy when a teammate is stretchered off and you don't exactly know what's wrong with him."[1][2][4][5]

Karetsas was well enough to watch from the stands as Dortmund dismantled Paderborn 3-0 on Saturday, and his return to full contact sessions puts him in contention for this weekend’s Bundesliga clash against Stuttgart.[2][4][7]

Dortmund invested heavily in the teenager this summer, paying Genk a guaranteed €30 million ($34.6 million) after he racked up 11 assists in 28 Jupiler Pro League appearances. He was brought in to fill the creative void left by Julian Brandt.[3][8]

For manager Niko Kovac, having his marquee playmaker back is a tactical lifeline. The club is already navigating the devastating loss of 23-year-old Giannis Konstantelias, who suffered a season-ending ACL tear in August.[3][4]

Tactical relief, however, remains secondary to the human element. Karetsas walked off a Champions League pitch on a stretcher and walked back onto the training ground eight days later—a massive win for the player, the club, and the sport.[2][7]