How is Lek's play off puck? Is he in position to cover for his line mates? Is he drifting into soft spots in coverage?
The first thing to say is that he hasn't been played in any sort of defense-specific role. He plays RW and hasn't had any PK time or been put on to defend leads late.
He isn't terrible by any means, he gets into the right spots, but is maybe a little tentative, which can lead to him being a moment behind in his reads. He is also one of the smaller, weaker players on the ice, so he is not going to outmuscle guys at this point and will have to win pucks with guile. That said, he skates well enough, has good hand-eye, and clearly sees the ice well, so with some physical growth you could project him as being a better defensive player than he currently is.
Lovely bit of skill, I was hoping someone clipped this. This clip also cuts off just before he set up another chance that went off the post (edit: maybe it was a save, hard to tell - in any case a good scoring chance for Leino - edit2: they just interviewed Leino after the second and he confirms it was a post, also says he is really enjoying playing with Lek).
Earlier in the period he made another nifty play were his stick was tied up along the boards, so he just dropped it, kicked the puck free and then made a kick-pass to his team-mate. This play led to another post (by Leino), so he is unlucky not to have been on the ice for a goal for thus far.
He has been directly involved in three good scoring chances so far, and his puck skills really stand out at this level.