West Ham manager David Moyes wants calm heads but not "vanilla players" in their Europa Conference League quarter-final against Gent on Thursday.
The Hammers lost to Eintracht Frankfurt in the Europa League semi-finals last year with Moyes sent off for kicking a ball at a ball boy.
Aaron Cresswell also saw red, with Declan Rice suspended for confronting the officials in the tunnel.
"We have to learn where we can draw the line," said Moyes.
"Emotions are something you never know what's going to happen. Looking back I can understand it, we were right up against it on occasions, but we've got to make sure we are better disciplined, calmer.