Sheffield Wednesday goalkeeper Chris Kirkland was attacked by a Leeds fan during a stormy 1-1 English Championship draw at Hillsborough on Friday.
Kirkland had just been beaten by a superb 77th-minute equaliser from Michael Tonge when Leeds supporters spilled onto the pitch in over-zealous celebration of the goal.
One of those fans ran up to Kirkland and, pushing both hands into his face, sent the stunned former Liverpool and England star crashing to the turf.
Police and stewards eventually cleared the field of the fans, but the visibly shaken Kirkland needed several minutes of treatment before he was able to continue.
The Leeds fans massed in the Leppings Lane end of the stadium also appeared to hurl objects, including broken seats, onto the pitch towards Kirkland.
Leeds manager Neil Warnock was quick to condemn the actions of his club's fans and he told Sky Sports: "I felt embarrassed to be a manager when I saw that, it was a disgrace.
"I'm very sorry about that. They should get the guy and put him in prison.
"There is no way he should be on the pitch doing that. When I see a moron like that I'm not proud to be Leeds manager.
"That person has the mentality of a five-year-old. He has spoiled everything. I've not seen anything like that before."
But Warnock's apology didn't placate Wednesday boss Dave Jones, who slammed the Leeds chief and his players for clapping the travelling fans after the final whistle.
"It was a great game but we are talking about vile animals instead," Jones said.
"You talk about racism in the game, but they were chanting things as well. I've had it for 12 years and it is just upsetting that they are able to do it.
"But to then go and wave at them. Not in my book. I've had a go at Neil about it. The authorities have to look at that. They should be punished for it."
Manchester United defender Rio Ferdinand, watching the Yorkshire derby on television, tweeted: "Wow, watching the Sheff Weds vs Leeds gamethat fan is a disgrace. Shocking. Been a good game too."
Stoke's former England striker Michael Owen also condemned the fan on Twitter.
"Oh dear. As if the game of football didn't have enough problems," he tweeted.
"For those not watching, Chris Kirkland (S.Wed GK) has just been attacked by a fan. Got to feel for Leeds fans. 1 idiot gives the rest of them a bad name."
Kirkland's ordeal came at the end of another turbulent week for football after several England Under-21 players were forced to endure racist taunts from Serbian supporters during a European Championship play-off.
That fixture, which ended in a mass brawl between Serbian players and coaches and their English counterparts, followed hot on the heels of the stain on the game left by the John Terry racism controversy.
Earlier this month, Chelsea captain Terry was banned for four matches and fined Â£220,000 after being found guilty of racially abusing QPR's Anton Ferdinand, despite already being cleared of the same charges in a court case.
Friday's incident came in a passionate clash between two of English football's sleeping giants.
Wednesday had taken the lead in the 44th minute when Jay Bothroyd headed home his first goal for the club direct from a long throw.
But Leeds equalised through Tonge's fine finish with 13 minutes remaining, sparking the sickening scenes that overshadowed the first meeting between the rivals for five years.