The suspect, who has been named on social media sites but not by police, has yet to be arrested after Kirkland was shoved in the face amid ugly scenes at Hillsborough. The FA is also investigating crowd trouble at the Yorkshire derby and is awaiting the referee's report.
Kirkland was assaulted by a Leeds fan after the visitors had equalised. The shocking scenes were broadcast live on Sky Sports and fans were quick to condemn the trouble on Twitter and Facebook. That led to a suspect being named on sites, and a mobile phone number being circulated.
South Yorkshire Police's senior investigating officer, Detective Inspector Mark Monteiro, said: "With the public's assistance we have clearly identified the offender who ran on to the pitch during last night's game between Sheffield Wednesday and Leeds United and who is suspected of assaulting the Sheffield Wednesday goalkeeper.
"We are dealing with the complaint made by the player and we are currently taking statements, collating evidence and making inquiries to locate and arrest the offender. We are also using CCTV footage from around the ground to identify suspects who may have been responsible for other offences before, during or after the match. I'd like to thank the supporters and general public who have provided information and assisted with our inquiries."
There were five arrests for various offences including public order before and after the game, while three people were ejected from the ground and 12 were subject to dispersal orders.
An FA spokesperson said: "An investigation is underway. The FA absolutely condemn the scenes that we saw [on Friday] night. The FA has been in touch with both clubs. Any individual found guilty of any violent conduct, we would expect the authorities to deal with in the sternest fashion, including football banning orders."
The incident occurred moments after Michael Tonge's goal in the 76th minute for Leeds made it 1-1. The fan ran from the away end to push both hands into Kirkland's face and then leapt back into the crowd. Sections of the travelling support also attempted to confront Wednesday fans, flinging bottles and ripping-up seats. Some chanted in praise of Jimmy Savile and aimed vicious barbs at Dave Jones, the Wednesday manager.
Jones described the Leeds fans as "vile animals" and called for them to be banned from attending all away games. While that is unlikely to be sanctioned, privately the FA also condemn the chanting. Of the chants aimed at Jones, relating to child abuse charges of which he was emphatically cleared 12 years ago, he said: "All the Leeds fans will be tarred with the same brush, and they should be, because from what I could hear it wasn't just one person chanting the vile things, it was quite a lot," said Jones. "You talk about racism in the game – what about the chanting? That is a form of racism – I've had it for 12 years, so I'll put up with it, but the club needs to clean its house out."
The chairman of the Leeds United Supporters' Club, Ray Fell, was critical of Wednesday for allowing the spectator to enter the field then abscond. He told Sky: "These clubs need to make sure the stewards works properly. The Taylor Report seems to have been forgotten in recent years and it's time we went back to looking at these things and that the grounds are properly policed and stewarded.
"The only hope for most of us is the police act quickly and this lad is brought to task for it. He let the club down and he let us all down. The only thing we don't like about it – it wasn't the Leeds fans who attacked the goalkeeper, it was a Leeds fan who attacked the goalkeeper and the other issue is also what fuelled it. Both sets of fans were chanting."
Of Jones' description of Leeds fans as "vile animals", Fell added: "I can understand his anger."
A Leeds statement said: "Leeds United would like to publicly apologise and condemn the action of the fan who came on the pitch and attacked Sheffield Wednesday goalkeeper Chris Kirkland. The club will fully co-operate with the police and the football authorities in identifying the individual concerned. After the week football has endured there is no place for this type of behaviour and the majority of Leeds supporters will be ashamed of his actions."
Immediately after the game, Neil Warnock told Sky Sports he felt Kirkland had gone down too easily, but later called on the culprit to be jailed. He said: "It's just so sad and disappointing. The club has made a statement and I'm pleased, we don't condone that. I hope the authorities and constabulary take the appropriate action. Get him sent to prison and stop it."
Yesterday Warnock, speaking to Sky Sports News, apologised for his post-match comment. Warnock said: "I was out of order saying that. There is nobody should be allowed to get on the pitch and do that to Chris. It's a minority who got on the pitch but you only need a small group, a few morons put everyone else to shame."
Warnock said that there had been offensive chanting by both sets of fans during the match. "I talked to the police afterwards. There were chants about Istanbul, Jimmy Savile, and I got abuse throughout the whole game. Dave got abuse too. I don't see how anyone can enjoy it."
guardian.co.uk © Guardian News and Media Limited 2010
image: © SMN