Burnley wore all black, including armbands, in memory of former Northern Ireland forward Jimmy McIlroy who died aged 86 on recently, National Daily learnt.
A Burnley fan was stabbed, and four others were injured, before the first leg of their Europa League play-off against Olympiakos in Greece.
The fan needed stitches to a leg wound and received medical attention at the stadium in Piraeus near Athens.
About 1,000 Burnley fans travelled to Greece for the game; 23 were held for being drunk and disorderly.
Burnley lost the game, the first leg of the Europa League play-off round, 3-1. The second leg takes place recently.
A statement from the club said: “The vast majority [of our fans] 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.
They beat Turkish side Istanbul Basaksehir and Scottish Premiership runners-up Aberdeen in extra time to set up the tie with Olympiakos