A Clarets fan was stabbed in Greece ahead of the Europa League play-off against Olympiacos at the Karaiskakis Stadium.
The victim is understood to have required stitches following the attack in Athens after being set upon prior to kick off.
Three other supporters were reportedly badly beaten and robbed as thugs targeted travelling fans.
Meanwhile, more than 20 Burnley supporters are believed to have been arrested for being drunk, disorderly and refusing to board coaches provided by the club.