Robert Lewandowski and Kingsley Coman were reportedly involved in a training ground fight on Thursday, with Bayern Munich yet to confirm or deny the incident.
A match-up against Fortuna Dusseldorf awaits on Sunday as the reigning German champions look to further cement their slim lead in the table.
However, this alleged incident between team-mates may threaten to disrupt that effort, with head coach Niko Kovac likely to address the situation at his pre-match press conference Friday.
Bild reports that during a private training session the players had to be separated by defenders Jerome Boateng and Niklas Sule after the 22-year-old French winger took issue with comments made by Lewandowski.
It is alleged that after the Poland international's remarks the players exchanged punches, with some being aimed at each other’s faces.
Even the intervention of their team-mates failed to cool things down as the two players continued to attempt to get at each other, the German paper reports.
Kovac is said to have initially considered continuing the training session at the Bavarian giants Sabener Strasse headquarters without Lewandowski and Coman, but eventually the head coach permitted the practice to proceed with both players remaining on the field.
That decision surprised other Bayern players, it is alleged.
Last year Lewandowski and Mats Hummels had to be separated after a fracas at a training session.
Lewandowski scored twice in Der Klassiker on Saturday, with Coman featuring from the start before being replaced by Franck Ribery in the 68th minute.
Lewandowski's first goal in that fixture was his 200th in the Bundesliga. Overall the 30-year-old has 21 goals in 27 league games this season.
Coman has featured 15 times for Bayern in the Bundesliga this campaign registering three goals and an assist.
Bayern know their hopes of claiming their seventh straight Bundesliga title rest in their own hands, as they hold a narrow-one point advantage over Dortmund.
The challengers could have temporarily reclaimed the top spot in the table by then with their fixture against Mainz taking place on Saturday.