Police have identified the Leeds United supporter who attacked Sheffield Wednesday goalkeeper Chris Kirkland during Friday night's 1-1 draw at Hillsborough.
The man, who has not been named by police, shoved Kirkland in the face following Leeds' equaliser during a match that was broadcast live on Sky Sports television.
He was identified by members of the public on social networking sites.
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 FC and Leeds United FC 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."
Meanwhile, Kirkland has spoken of his shock at being attacked and urged the authorities to take swift action to prevent a repeat.
The former England keeper said in a statement released by Wednesday: "I was gutted with conceding the goal and had my head down as I kicked the ball down the field so we could restart the game.
"I was looking at the ground but when I looked up, I caught a glimpse of someone coming towards me on the pitch. I thought he was going to give me some abuse but then suddenly he came at me with both hands and I was stunned. I felt the full force and I was just shocked because you never know what could have been in his hands.''
Kirkland was treated by Wednesday's medical team and was able to complete the match.
He continued: "I was sore and, as I say, really shocked at what had happened. My mind then turned to the possibility of winning the game because we had played ever so well and there was still 15 minutes to go.
"The rest of the game flew by and then the final whistle came, the adrenalin goes and you reflect on something like that and it was scary. I thought of my family watching something like that and it was not a nice feeling to think my daughter saw me assaulted like that.
"I just want the authorities to look at what happened and take the appropriate action because sooner or later, we could be talking about something even more serious.''
The Football Association had earlier said it would investigate crowd trouble during the match.
A spokesman for the governing body said: "We are investigating the events of last night and awaiting the referee's report. The FA condemns the scenes at Hillsborough last night. We have begun an immediate investigation and have been in contact with both clubs.
"We would call for the authorities to identify and bring before the courts anyone who was involved in any form of criminal disorder."