Bayern Munich players Robert Lewandowski and Mats Hummels argued at training on Wednesday, with Hummels accusing his teammate of being sluggish and telling him to "shut up."
Bild reported that Lewandowski decided to tie his shoelaces rather than defend during a training match, leading to a bust-up between the two former Borussia Dortmund players.
"Lewy, are you serious? You are doing shoelaces? Holy s---," Hummels reportedly said, before Lewandowski replied: "And you've lost the ball."
Hummels later questioned the striker's attitude and Lewandowski responded by questioning Hummels' ability before the defender said: "Shut up. Get lost!"
The disagreement occurred amid reports of Lewandowski's possible departure from the Allianz Arena after he changed agents last week.
Afterward, Hummels played down the incident, saying it was a routine disagreement.
"It's nothing big," he told Bild. "It happens all the time."
Lewandowski, who joined Bayern from Dortmund in 2014, hired Pini Zahavi as his agent, renewing speculation that he could make a big-money move to Real Madrid, Manchester United or Chelsea.
Holding midfielder Sebastian Rudy, meanwhile, has told kicker that he does not think about leaving Bayern in the summer.
Having only joined on a free transfer from Hoffenheim last summer, the Germany international has been struggling for minutes in recent weeks and did not make the squad for the matches against Schalke or Besiktas.
"I did not come here only to leave after one year," Rudy said, adding that he remained confident of receiving a call up to Germany's World Cup squad by coach Joachim Low.