Matt Simon faces a suspension for shouldering Melbourne City defender Michael Jakobsen in the head after the A-League's match review panel issued the Sydney FC striker with a show-cause notice.
Substitute Simon had barely been on the field for a minute late in Friday night's 1-1 draw at the ANZ Stadium, when he became involved in a fiery confrontation with Jakobsen.
The pair had to be separated several times but one particularly ugly incident in the 82nd minute, apparently missed by referee Kris Griffiths-Jones, prompted action by the panel on Monday.
Moments after the Sky Blues were awarded a free kick for a Jakobsen foul on Simon, the 30-year-old appeared to throw his shoulder into the Dane's head, knocking him to the ground.
Simon has until 1 p.m. local time on Tuesday to make a submission in response, after which the panel will decide on any possible punishment.
Should he be banned, the regularly used substitute will at least miss Saturday's away clash with Perth Glory.
Meanwhile, Melbourne Victory winger Jai Ingham has escaped sanction for stomping on the leg of Western Sydney Wanderers defender Jonathan Aspropotamitis.
Ingham stood on Aspropotamitis' leg and then stomped on his calf during Victory's 3-0 win at the ANZ Stadium on Saturday night and, while he received a yellow card, there was speculation over whether referee Chris Beath had missed the second action.