I think with Karlsson, things came relatively easy for him in his twenties. He was so naturally gifted that he didn't have to think too much about it. Now that he's thirty, it's not coming so easy. For thirty year olds, to stay in the upper echelon of star players, they have to train like beasts and live in the gym. Not to mention the diet and lifestyle they have to maintain off the ice.
I am guessing this is not Karlsson.. I don't know this for fact, but I suspect he doesn't have the work ethic needed to be a star player in his 30s.