I thought about Maatta, but he hasn't produced in either of the previous 2 WJC. Mind you in his first year he was the 7th dman and didn't get much playing time.
Maatta flipped a switch and has been a more prolific offensive player since the OHL playoffs last year. Plus, he'll be eating the most minutes behind the best grouping of forwards Finland has had in a while (certainly since the Rajala, Pulkkinen and Granlund trio).
Don't be shocked if he's a PPG defenseman this year.