Even if you manipulate the list with that criteria I see at least 3 in Kokkonen, Niemela, and Villenueve.
I don't understand why we're removing the not yet graduated guys though. Does Sandin and Liljegren playing in the NHL next year make it more likely we're going to need defenceman in the future than if they start to stagnate a little bit and stay in the AHL for another year? We still control them until they're 27 either way which is 6 and 7 years away.
Similar question for Lehtonen. We have a young defenceman, regardless of whether he's on a prospect list or not having him in the system reduces the need for a defenceman in the future if he works out. I obviously didn't include Dermott, but the same logic holds there. A team with Dermott needs 1 less D for the next 5 years than a team without Dermott and that doesn't show up on prospect lists.