You don't need to be a rugby or league purist to know the games are poles apart when it comes to defensive and attacking structures.
Blues coach Sir John Kirwan has talked about the adjustments Marshall will need to make from going from a one-dimensional game to a three-dimensional one: "Suddenly, things will be coming at him from all directions and there's serious decisions to be made."
Marshall has made similar comments. He is quick to point out that in league you are a left or right-side player but in rugby you need to be both. His instinct in league was to step inside to find space, but to do so in rugby would mean being quickly smothered.
He has been quoted as saying he was frustrated in his first week of rugby because he wanted to be good at it but wasn't.
But silencing the doubters isn't on Marshall's mind.
"I don't really care, that doesn't fuel me. What fuels me is wanting to perform and wanting to be the best. I don't have to prove anything to anyone other to myself and my team-mates."
The popular notion has been that Kirwan will field Marshall on a regular basis at fullback, as much because of the greater space he would have there to cut his attacking capers as anything else. The latest word, however, is that he will share the first-five responsibilities on Saturday with up-and-comer Baden Kerr.
Kirwan has had Marshall at No10 in training over the past couple of weeks and has been delighted at his response to the pivotal role.
"The last two weeks have been really intensive but he's blended in fine. He has been playing a lot at 10, hasn't done much at 15, and so far, so good. He's doing everything he can ... and we just need to get him out there to have a bit of a crack at it."
At the same time, however, Kirwan is urging rugby fans not to put pressure on Marshall to become a great player in week one.
"I think he will be a great rugby player but it will take him a little while to get used to the finer parts of our game. This is a long-term project and we think he's going to be a good 10, so we'll just go with that."