Cornier mixes up his guard like an older Foreman did in the 80`s and 90`s, I watched a vid by modern martial artist youtube channel where this is mentioned, should more MMA fighters sought advice from boxers on how to mix boxing in with their other fighting skills?
Possibly. But Foreman's guard generally works for powerful punchers, aka Big George himself, Witherspoon etc. Cormier is a good puncher but not particularly exceptional in that regard. I could see that guard working for him during certain periods of the fight. However, he couldn't rely on it all the time because the guard doesn't allow for good counterpunching.
He uses his guard like Foreman and went to him for fighting tips. Using boxing skills is very important in MMA fights studying boxers would be very helpful.
