Hampshire Police launch assault investigation after Portsmouth fan appears to kick Sunderland's Luke O'Nien
The 24-year-old tumbled over the barriers separating the Fratton Park pitch from spectators during the second half of the Black Cats' play-off semi-final with Portsmouth.
And he then appeared to be kicked by a member of the home support, with videos of the incident spreading like wildfire.
O'Nien's team mates - including Lee Cattermole and Grant Leadbitter - quickly leapt to his defence and exchanged some views with the Portsmouth faithful.
An increased police and stewarding operation was seen around the area where O'Nien crashed over the barrier following the incident, with some reports suggesting the supporter was ejected from the ground.
Police have now confirmed that an investigation is underway into the incident - although no arrests have been made as of yet.
Hampshire Police said on Friday: "We can confirm we are investigating an assault against a Sunderland player at the Portsmouth v Sunderland football game at Fratton Park last night (Thursday, May 16).
"No-one has been arrested at this time."
O'Nien spoke to Sky Sports about the incident after the game, and confirmed that he would not be pressing charges.
The full-back laughed off the incident, saying: "I kind of went over the boarding.
"They had a few digs at me, but that's just football.
"Yeah [the police have spoken to me]. They asked if I wanted to press charges, but that's just football.
"When the whistle goes, it's two teams going at it and two crowds going at it and that's a massive part of it.
"Yeah, there was a little bit [of contact].
"It was what it was, but he didn't hurt me or anything like that. I think he got arrested in the end, but he can have that one!"