I don't know...even IF Kakashi managed to "chidori his heart out" Zaraki would pull SOME sort of basass reversal, like Ichigo pulled against Ulquiorra. I guess it all comes down to who we can see losing. It's pretty easy to see Kakashi defeted, since he did get his ass handed to him a few times. It's much harder to see Zaraki going down, since even the one time he DID go down...it still didn't look like loss. But granted, Zaraki only fought three times in the series: VS Ichigo (draw), VS Tousen (win) and VS Nintora (win), so it's pretty easy to see him as either winning with no effort, winning while taking huge damage, or a double KO. I just can't see Zaraki losing.