Just based off of my personal experience, back when Uncle Tryhard was in the infantry and starting out in BJJ the cardio base I had from running and aggro PT sessions definitely helped me keep pace with far better, infinitely more experienced grapplers. I understand that grappling wasn't fighting, but road work and a healthy lifestyle are absolutely huge in terms of keeping you fit to do anything. This is just one man's opinion, but I truly feel that's how it plays out for most fit people in the real world.
Without question, the Diaz boys are some of the fittest fighters on the planet and I have to believe that their triathlon training is huge in terms of having developed an unbelievable cardio base. Their controlled fighting style and naturally psychotic personalities are huge factors too, but at the end of the day these guys are all around cardio outliers in this sport and I don't see cardio being the determining factor in this fight. Nate will show up in pretty good shape. The reason he will very likely lose has more to do with the lack of quality fight-specific preparation he has put in. His reflexes will be a little slower, his mind may very well not be in the right place because he hasn't had the necessary time to get ready, and he just hasn't had the necessary time to surround himself with speedy southpaws to help simulate McG's style and formulate a winning game plan (what, you don't think the Diaz' game plan?).
Also, Conor's really freakin' good and should be coming in on point and rarin' to go. That part's key.
I don't know who to cheer for in this. So long as it's a good fight, and I think it definitely will be, I'll be a happy man. Would've loved to see Nick in there instead. If Conor could outstrike him I may well have to rename my first born McG.