I only watched the first period and a bit of the second before switching to a different game. In the bit I watched, Tolvanen seemed to struggle a little. It's nothing too concerning, but early on he made two passes into the receivers' feet and on another sequence he was sort of floating near center ice and the puck went off his skate sending the Sabres the other way on a rush. And then shortly after that he went soft into the boards to get a puck and easily lost the puck battle. I noticed that Laviolette benched him for a couple of shifts after that.
It wasn't all bad, though. He did back check nicely a few times and he seemed to really be focusing on his positioning in the defensive zone (something I assume the coaching staff has been working on with him).
Considering this was only his 5th NHL game, my observations are nothing to be too concerned about. He clearly has some skill, and with enough time I think the deficiencies in his game can be rectified. He is still very young and the commentators mentioned that Laviolette has been impressed with his attitude and work ethic in practices. Some might think that's just lip-service, but Laviolette doesn't strike me as the type of coach that would compliment a young player like that unless it was deserved. If anything, he has a reputation for being very hard and demanding on young players, so I will take those words at face value.