Lothar Matthaus was left disappointed after the game with defender Mats Hummels’ actions off the pitch, rather than on it.
Mats Hummels spent seven years at Borussia Dortmund, having initially spent a season on loan at the club from Bayern – before rejoining his boyhood club this summer.
It is understood the Bayern defender visited his former teammates in what used to be his home dressing room, before seeing his side fall to their first defeat defeat of the season.
“I would not forbid Mats Hummels if I was the present coach, but would suggest that takes place after the game,” Matthaus admitted.
“Before the game, the concentration should be on the game and not the old friendships.”