Police and the Football Association launched an investigation after a Stevenage player was punched, apparently by one of his own fans, as he celebrated the club's shock FA Cup victory over Newcastle.
Defender Scott Laird was floored by the blow as fans ran on to the pitch at the final whistle as the League Two side celebrated yesterday's 3-1 win over their Premier League opposition in the live televised match.
Videos of the incident were immediately circulated on the internet.
The grainy image shows Laird celebrating on the halfway line following the game.
He is suddenly approached by the fan who punches Laird directly in the face, knocking the player to the turf.
Stevenage manager Graham Westley confirmed that Laird had been poleaxed by the blow in an incident which marred the most glorious night in their history.
Westley said: "Scott Laird was stood celebrating with the fans and a fan just came over and smashed him from the side.
"He went to the ground and it is a shame for the afternoon to end in that way.
"He is a bit bewildered. He (the fan) gave him a right-hander, just smashed him across the cheek and knocked him to the ground.
"He said to me, 'It's lucky I've got a big head to take it'. It was a sad way for things to end."
An FA spokesman said: "It's something that should be flagged up in our meeting on Monday.
"It might be that there was a stadium adviser at the game who'll be able to advise us on that."
Police have described the fan as a white male wearing a white Diesel top and red and white Stevenage scarf.
A Hertfordshire Police spokesman said: "Police are investigating an incident after the match between Stevenage and Newcastle United.
"It is believed a Stevenage fan assaulted a Stevenage player."Reuse content