West Midlands police are appealing for witnesses after one of their officers was "seriously assaulted" before England's Nations League game against Hungary on Tuesday night.
A statement from the police stated: "The PC - who works with our Football Unit - was behind Molineux Stadium's Stan Cullis stand at around 7.25pm when he was attacked.
"It's understood he was approached from behind by a group of men on a grassed area and hit in the side of the head. He was knocked unconscious, suffered a head injury, and was taken to hospital for an assessment and treatment.
"We're assessing body-worn video and CCTV in a bid to identify who's responsible.
"Four men, aged 21, 20, 19 and 18, were later arrested nearby on suspicion of assault and they remain in custody for questioning."
Anyone with information is asked to message us on Live Chat through our website or call us on 101 quoting log 1554 from 14 June.
Detective Inspector Kate Longbottom from West Midlands Force CID said: "We've spoken to some witnesses but potentially many more people were in the area and saw what happened or the offenders running off.
"We really need to speak to them as they could have important information; I would ask them to get in touch as a matter of urgency.
"There was a good atmosphere in the build-up to the game, high spirits and lots of families enjoying the occasion. That's what made this assault even more shocking as it appears to have been totally unprovoked."
England ended up losing the game 4-0 which prompted boos from sections of the home faithful at full-time. Rolland Sallai's brace handed Hungary a two-goal cushion midway through the second-half after John Stones was given his marching orders.
Adam Nagy and Daniel Gazdag struck late on as England slumped to the bottom of Group A3 and face relegation to the second tier of the Nations League. Meanwhile, Hungary have moved to the top with their second win over the Three Lions in just 10 days.