A Burnley supporter was stabbed in the leg on Thursday night as their Europa League tie at Olympiacos turned nasty.
Sportsmail understands the Clarets fan required stitches after being set upon with a knife outside the Karaiskakis Stadium.
Three others were badly beaten and robbed and those following Sean Dyche's side warned of locals carrying knives before the 3-1 defeat in Greece.
Twenty-three Burnley fans were also arrested for being drunk, disorderly and refusing to board coaches provided by the club.
Dyche faces an uphill task to progress to the group stage and the manager claimed he witnessed intimidation of referee Slavko Vincic in the tunnel at half-time with the game at 1-1. Olympiacos were awarded a controversial penalty and Ben Gibson was sent off after the break.
'The scenes I saw at half-time from all and sundry, and then things change in the second half,' Dyche said. 'They were waiting for the referee. You all saw the feel of the game was different in the second half.
'We are told to respect referees. I feel for our fans, they've come a long way to see a balanced game and haven't seen that.
'Hopefully next week will be more even. There is no disrespect from me. I'm telling you factually on what I saw. You tell the truth and that's exactly what I'm doing.'
Burnley praised the behaviour of their 900 supporters in Greece in a club statement after the match, however revealed that five people had been hurt.
It said: 'The vast majority were once again impeccably behaved, with the coaching operation to transport supporters to the ground put in place by the club again a great success, as it was in the previous round in Istanbul.
'However, five of our supporters were unfortunately injured – including a person who received a stab wound to the leg – and received medical attention at the stadium.
'Those injured all travelled independently to the stadium, outside the organised travel operation.
'Burnley is working closely with Olympiacos and the local Greek police to investigate these incidents.'