I included all my scouting reports in the beginning of this post.
None of the three players -- Slafkovsky, Jiricek or Nemec -- are *elite* skaters. But they are all very good skaters. With Slafkovsky and Jiricek in particular, we have to factor in not only speed, but balance, edges and how strong they are on their skates. Slafkovsky and Jiricek are both pretty much immovable objects.
Will Slafkovsky be fast enough to be the driver in transition? No -- but the Devils won't want him to. He'll be linemates with an elite zone entry guy like Hughes or Bratt, and his job will be the force down low -- creating traffic in tight and creating more room up high for the skill guys to work their magic.
The most enticing aspect is that Slafkovsky also possesses elite puckhandling skills and passing vision. Once this guy wins the puck down low -- which he does an extraordinary percentage of the time -- he can use his size and hands to create room and space for himself, then possesses the vision to thread high-anticipatory passes on an elite level.
So, as
@Jason MacIsaac correctly pointed out -- Slafkovsky is easily "fast enough". His speed isn't necessarily
what he beats you with, but it plays up alongside his size/strength and can still beat you outside simply by pulling the puck off his body and holding you off with his free hand and enormous frame. He's also capable of bullying to the net front, especially against smaller and more-finesse-based defenders. If he is combined with Jack Hughes, they will create an abject mismatch every time they hit the ice together.