Seppanen has played his junior years in IFK Helsinki. The metropolitan market has gained him some visibility, but on the other hand he has had to fight for it with many quality prospects. He has won both the Jr C and Jr B Finnish championship titles with IFK. Seppanen went undrafted after being a positive surprise at times and inconsistent at others in the U18 WC of 2005. He moved right on to the U20 national team and made the WJC squad against early expectations. In the spring of 2006 Seppanen was very strong in international practice tournaments and in his domestic pro debut.
2007-08: The biggest accomplishment for the slick Fin this past season was staying in the SM-liiga for the first time in his pro-career, a signal that he has taken a major step in his professional development.
Deep down Seppanen is a simple defenseman by nature, whereas on the surface, as evidenced by the things he at times does on the ice, he isn't. Although he may not have the most imposing frame or the flashiest puck skills, he is still often seen generating a scoring opportunity or mucking near the own crease. However, Seppanen is not very far long along in development in decision-making. He is a strong shut-down defenseman without the puck but vulnerable when attacked by forecheckers. There is still a lot to learn about reading the play at high levels before he can become a strong all-around defenseman.
Seppanen may get an invite to the Penguins training camp for this upcoming season, but it seems more likely he is to go back to the SM-liiga at least for one more season to continue his development.