The former Ajax man had also been training with Hull City and Celtic earlier this summer as he looked to secure a deal, but work permit issues stood in the way of him landing a contract at either club.
Claasen has since joined Polish side Lech Poznan and Blackpool secretary Matt Williams explained that a move to England would have been complicated for the 23-year old.
"We made him a very decent offer, subject to him gaining a work permit, but he didn't accept," Williams told The Blackpool Gazette.
"We'd only seen him play 20 minutes against Newcastle and in a training match at Preston, so we weren't prepared to go any higher. We wanted another look at him against Bury on Tuesday but he didn't want to play.
"There were no guarantees he would be able to get a work permit and that was reflected in the offer we made him.
"As Hull also found out, this would be a very difficult process, so we shook hands and wished him well for the future."