Bayern Munich striker Robert Lewandowski, who is one short of the Bundesliga's all-time goal record with two games left, broke off team training early on Thursday, the club has confirmed.
Lewandowski has scored 39 league goals this season - one short of Gerd Mueller's Bundesliga record of 40 set in 1971/71.
However, Bayern's star striker only trained for 40 minutes on Thursday ahead of Saturday's away match at Freiburg.
In a statement, Bayern said Lewandowski "trained a little shorter than the rest of the team" because of his work load having been sidelined for three weeks in April by a knee injury.
However, German daily Bild reported the star striker suddenly pulled up and had to stop training, while looking visibly annoyed.
Both Bild and magazine Kicker say Lewandowksi left the training pitch accompanied by team doctor Jochen Hahne and physio Gianni Bianchi.
It was the first day of a special training camp which Bayern, who were confirmed Bundesliga champions for the ninth straight season last weekend, are holding in Grassau am Chiemsee, near Munich.
All top-flight German league clubs are holding a quarantine camp for the last two matches of the season in the face of the Covid-19 pandemic.
After this weekend's away game at Freiburg, Bayern host Augsburg week next Saturday in their final league game of the season when they will be awarded the Bundesliga trophy.