The Finns finished third in their World Cup qualifying group, behind Spain and France, and took a point off the reigning world and European champions in March.
However former Hibernian boss Paatelainen sees them as underdogs with Wales having the likes of Gareth Bale and Aaron Ramsey in their side.
He said: "We hope we have a proud and energetic performance but we realise Wales are a quality team and individually their players are top class.
"If they perform to the best of their ability, and we do, we have no chance.
"But football does not always go like that and we hope our players have a good day and Wales' players do not.
"Stopping Ramsey and Bale will be key. Ramsey is a wonderful midfielder and Bale's pace and goalscoring ability is fantastic, but there are other players too.
"Joe Allen is in the squad again and is keen to carry on his quality of performance for Wales.
"They have players coming back who were not there in their last qualifying matches, and they are eager to show how good they are.
"Their manager has also signed a new contract - congratulations to Chris (Coleman) - and that is very important.
"Chris has been in charge for two years and started in a very difficult situation but he has lifted the team and I think Wales will go from strength to strength in the coming years."
Paatelainen is hopeful that Rubin Kazan midfielder Roman Eremenko will be available after a dental problem and otherwise he has a fully-fit squad to choose from.
He said: "We have hungry players who want to learn and establish themselves as regulars at their clubs. We improve all the time and have achieved some good results so hopefully this game can be the same even though it will be very difficult."
Watch Wales take on Finland live on Sky Sports 2 HD from 5.45pm on Saturday.