The Finland international feels the Amsterdam giants face an impossible task if they show their opponents too much respect
The Eredivisie champions start their European campaign with an away game against the Spanish giants and the Finland star feels they don't stand a chance if they travel to Spain with fear on their mind.
"We shouldn't show Barcelona too much respect and must try and get a good result," he told De Telegraaf.
"We cannot afford to be afraid of them, because you will definitely lose if you show fear."
The Finland international then went on to stress that Ajax must improve on their performance against PEC Zwolle at the weekend if they are to stand a chance against Barca.
"If we allow Barcelona as much space as we allowed Zwolle, Lionel Messi will have 10 one-on-ones with our goalkeeper.
"If we defend at Camp Nou like we did against Zwolle, every chance will be a goal."
Wednesday's match will be the first time Ajax and Barcelona meet in an official game.