Franck Ribery was on Wednesday involved in a slanging match with an angry fan at Bayern Munich's training ground, the club said, amid reports that the player had been asked to look after the supporter's dog.
The Bundesliga leaders said that the fan talked his way past security staff and into the team's dressing room in south Munich and the pair argued in French before the imposter was ejected and banned.
The club contacted the police, who identified the fan as French from his car registration.
German media reported that the fan had left his dog at Bayern's training ground in January with a note attached for the attention of France winger Ribery, asking him to look after the animal, a female called Oito.
"Dear Franck, I'm very sorry. I don't know who I can turn to anymore," the letter reportedly began.
"For a few weeks I've been looking for a solution for Oito, who's been classed as a fighting dog. But you won't find a sweeter animal. I'm a bit ashamed about this but I'd be very happy if you could do something for Oito," it reportedly continued.
The France star knew nothing of the incident before being confronted on Wednesday, the club said. The dog has since been taken to a shelter for abandoned animals.