Schalke forward Rabbi Matondo has apologised after a photo posted online showed him wearing a Borussia Dortmund shirt, emblazoned with Jadon Sancho's name and number, while taking part in a gym workout.
Dortmund and Schalke are arch-rivals in Germany's Bundesliga, and fans of the Gelsenkirchen club were unhappy to see one of their players wearing the kit of one of Borussia's star players.
Matondo apologised on Instagram, with the 19-year-old Wales international stating that he had not wanted to cause anyone "grief or trouble".
He wrote: "I am very sad and disappointed in myself that I have let down anyone who feels connected to Schalke.