In this case it makes all the difference. He wasn't "joking," but he was hyperbolizing his opinion in private, which is a big nothingburger. If in a press conference, somebody asked him his opinion of "opener's" perhaps he would just say "I don't like the idea." Which is probably the same opinion as 90+% of every other 29+ year old MLB pitcher who has been a "starter" his entire career. Part of what has made Bumgarner an ace is a certain type of bullheadedness. Sometimes, that's bad (throwing at Braun last year...in a meaningless game for the Giants mind you). Sometimes that's good--being a dominant ace on 2 World Series Champions and a significant contributor on a third. There is a possibility that if you take away that emotional stubbornness that can sometimes result in minor negatives you run the risk of also taking away the edge that makes him a potential HOFer. That type of attitude is certainly not worth the risk on a marginal talent, but Bumgarner isn't a marginal talent. Still, it's just part of his entire package that one would take into account when ascribing what his value would be in a trade, but it's not something that you would write him off as a complete bonehead for, or as a reason why you would have no interest in having on your team no matter what.