Well, his OHL team was in the playoffs up till a couple of games ago, while Greenway was done what, 3 weeks ago?
Also, Greenway can slot it on the bottom six and just by size alone be a factor. Sokolov is a sniper to whom checking is a rumor, and is said to have slow feet by NHL standards. Don't see him knocking off anyone on our top 2 lines at this point. For all his success in the OHL, he is considered to be a project. Making the jump without any training camp or practice to the NHL is only for the chosen few. Going from OHL to the NHL is basically jumping up three levels( some would say 4)
OHL>NCAA>(ECHL)>AHL>(KHL)> NHL
A guy like Kaprizov who is starring in the KHL could probably jump straight into the lineup and not embarrass himself, but it's tough for even an NHL'er to come into a new team mid season and start being productive right away.
Greenway's effectiveness( and it's not like he's been great) is all about his size and strength, which is needed against a team like the Jets.