Frank De Boer is optimistic that the tiny percentage of Ajax fans he describes as "crazy" will not disrupt tonight's night's encounter at the Amsterdam ArenA.

UEFA opened disciplinary proceedings against the Dutch club after some of their supporters fought with police and stewards during the 2-1 defeat at Celtic Park a fortnight ago.

Evidence of damage to seats in the away section also came to light after "instances of disorder" were dealt with by police in Glasgow ahead of the match. The case will be dealt with by UEFA's control and disciplinary panel on November 21.

Speaking on Tuesday at the pre-match media conference at the Ajax stadium, the Dutch coach praised his side's supporters for the way they backed their team at Parkhead, saying, "there were moments when they made more noise than the Celtic fans did which was fantastic".

However, De Boer said that some Ajax fans remain a concern when asked if he was confident of the game passing off trouble-free.

"I am confident in that but you never know," said the former Rangers player. "There is always some crazy people [who] try to disturb something but hopefully it will not happen. There have not been so many incidents like that over the last couple of years. Of course, it was a bad thing they did in Glasgow and hopefully they will be punished for that but normally 99% are good supporters."

De Boer is aware of the importance of the game against the Scottish champions - victory is needed if they are to have a realistic chance of playing European football in the new year - but admits the sad news about his former Ibrox team-mate Fernando Ricksen puts the importance of football "into perspective".

Ricksen, 37, announced last week that he is suffering from motor neurone disease.

"It is quite sad that a colleague a little bit younger than me has that disease," said the former Ajax and Netherlands defender. "I feel sorry for him. He will get a lot of support from his family and ex-colleagues. That puts everything into perspective. We have to realise that football is a nice game but there are more important things in life than three points."