Bayern Munich stars Frank Ribery and Bastian Schweinsteiger were involved in a training ground mishap which left the French winger hobbling off for treatment.
Preparing for the journey to Mainz, the Bayern squad was training in a match simulation when Schweinsteiger lashed out at Ribery and caught him high on the shins.
Ribery fell to ground as play continued around him before shuffling off the field and seeking the attention of Bayern staff.
Ribery has scored four goals and made 14 appearances this season for Bayern.
Bayern and Mainz encounters are always tight affairs, and it is no surprise to Bayern players to see such commitment on the training paddock.
"It's always been tough in Mainz in recent seasons," Bayern's David Alaba told FCBayern. "They keep it tight and they're always aggressive. We'll have to resist."
Any injury to Ribery would be a massive blow for the Bundesliga leaders, with Xherdan Shaqiri and Rafinha already ruled out for the trip.