The police are investigating a video on social media which it is claimed shows Sheffield United’s Oli McBurnie stamp on a fan during a fracas.
It is not clear if McBurnie makes contact with anyone and the circumstances are unknown.
A Twitter user said McBurnie, who is injured, looked “more like he was trying to step over him with one bad leg”, to which he replied “100%”.
Sheffield United declined to comment.
The incident, which is also being investigated by the Football Association, occurred after fans invaded the pitch following the Blades’ Championship play-off semi-final second leg defeat at Nottingham Forest.
Scottish striker McBurnie, 25, missed the game with a foot injury he sustained in April.
Inspector Andy Wright, of Nottinghamshire Police, said: “We have been made aware of a video circulating on social media showing a possible altercation where a Forest fan can be seen on the ground following the play-off semi-final.
“We have now started an investigation into this incident.
“The person in question has not yet reported the incident but would urge them to come forward along with any other persons who many have witnessed the incident or have video footage so we can establish the full circumstances.
“We would particularly appeal to the owner of the original footage to make contact.”
In a separate incident, police have charged a man after Blades captain Billy Sharp was allegedly assaulted at the end of the game.
Forest won 3-2 on penalties after the two legs finished 3-3 on aggregate.
The Professional Footballers’ Association (PFA) has called for a review into matchday security and fan disorder following the incident involving Sharp.
The EFL condemned the pitch invasion at Forest, and has warned it could consider measures including capacity reductions should such similar occurrences happen in future.