The German Football Association have confirmed they are investigating Werder Bremen midfielder Diego for alleged violent conduct towards the end of yesterday's Bundesliga defeat at Karlsruhe.
The Brazilian apparently grabbed Karlsruhe's Christian Eichner in the aftermath of a melee which also saw his Werder team-mate Claudio Pizarro sent off.
Referee Guido Winkmann did not see the incident involving Diego, meaning the German FA (DFB) can take retrospective action.
The DFB will view television images on Monday before announcing their verdict.
If found guilty, the 23-year-old Diego can expect to be suspended at least for his side's final Bundesliga game of the year against Wolfsburg next weekend.
Pizarro can also expect a lengthy ban for his red card having lashed out at Martin Stoll at the end of Bremen's 1-0 defeat.