I don't think that Magsayo needs to be careful in this fight, I mean he has nothing to lose here.
So he might as well go all out and make it a war against Russell. Of course this is not is hometurf, nevertheless I think the judges should be fair enough to call him the winner if indeed he will be the close victor in this fight.
Definitely a clean KO would be good and we all wanted that to see, but if it goes to the judges hand he can also have a good chance to win.
We can only hope and see if what will happen if in case a decision needs to be called, a fair one will be nice for Magsayo, this would be a good opportunity for him to open a much wider door for his career, he needs to showcase all the talents that he got to fight tough by tough with Russell, like what you have said, he don't have anything but the hope that he can upset Russell and start a brand new direction to his career.
Will needed to wait and see if what Magsayo will bring in this upcoming fight.