The health of Konstantinos Karetsas is dominating the conversation at Borussia Dortmund after the 18-year-old collapsed on the pitch during Tuesday's Champions League opener against Villarreal. Two days on, he remains in hospital with no confirmed diagnosis. Sporting director Ole Book said further tests are ongoing and that the club wants to "get to the bottom of things," while stressing there is no indication the situation resembles Christian Eriksen's cardiac arrest at Euro 2020. A Belgian report citing dehydration as a possible cause has not been officially confirmed.

The incident overshadowed what was otherwise a positive result. Dortmund came from behind to beat Villarreal 3-2 at Signal Iduna Park, earning a winning start to their European campaign. New signing Joey Veerman was outstanding, registering 99 touches and completing 82 of 87 passes in a performance that drew comparisons to Toni Kroos and Andrea Pirlo. Serhou Guirassy was the match-winner.

The injury situation beyond Karetsas remains serious. Giannis Konstantelias is out long-term with a cruciate ligament injury, while Nico Schlotterbeck, Emre Can, Filippo Mane and Ramy Bensebaini are also unavailable. Ethan Nwaneri, on loan from Arsenal, has stepped in as cover for the attacking positions.

Dortmund sit third in the Bundesliga with six points from two games and host promoted Paderborn on Saturday, though Karetsas will play no part as his recovery takes priority.