The German Football Association has asked Hoffenheim forward Ryan Babel to explain comments published on his Twitter account in which he criticised referee Thorsten Kinhofer, who sent him off at the weekend.
Babel was shown two yellow cards in a matter of seconds in his side's 3-1 defeat to Hertha Berlin on Saturday.
On his Twitter account, he claimed the "ref was on drugs", leading the German FA (DFB) to open proceedings against the Dutchman. He will give his version of events before the DFB will decide what, if any, action to take against him.
Any additional suspension to the automatic one-match ban for the red card would be carried over to next season since the current campaign has now ended.
It is not the first time Babel has been in bother for his use of social networking websites.
His photomontage of referee Howard Webb wearing a Manchester United shirt last year earned him a fine from the English FA while he was on the books of Liverpool last season.