Ruben needs the win a lot more than Montanes does. But that's besides the main point which is both are going to come to win, and it's a great opportunity for both, but especially Ruben since he doesn't get to this stage in majors often.
Montanes is no Cilic. Ruben won't get any free points from errors, unless Monty is diabolical, which he doesn't seem to be. Montanes is the clear favourite, and I expect him to defend his points here.