Eintracht Frankfurt board member Philipp Reschke on Thursday condemned fan violence before the Champions League match with Napoli, saying "it hurts football".
A group of around 300 Frankfurt ultras clashed with police and Napoli fans on Wednesday before the second leg of the sides' last 16 tie.
Six police officers were injured in the violence, while three Frankfurt fans were among eight arrested during the clashes.
Napoli won the match 3-0, going through to the quarter-finals 5-0 on aggregate in what was Frankfurt's first ever Champions League campaign.
"We deeply regret the events that have taken place here. There is absolutely nothing to justify this violence... it is unacceptable," Reschke said before the team boarded a flight back to Frankfurt.
"It harms football, it harms Eintracht Frankfurt and it harms our efforts to stick up for fans who want to watch a game without restrictions in the stadium."
Frankfurt fans were officially shut out of the stadium for the match by authorities in the prefecture of Naples. The club criticised the measure and has launched a lawsuit, which has been backed by UEFA.
Frankfurt coach Oliver Glasner said on Thursday he condemned "all forms of violence and crime" while sporting director Markus Kroesche said "things like that don't belong in football".
