User blog comment:IamJakuhoRaikoben/Chapter 373: Life or Death?, Review./@comment-24039250-20140228131505/@comment-24039250-20140228133254

The fact that Zeref speaks of how Natsu might win against END proves to me how he is not END. How can Natsu fight and beat himself. Unless we are doing some "Tailbeast battle inside mind" thing I don't see that a possibility. I'm not trying to rip on the theory, and in truth the theory isn't a bad one and would be interesting if it was true, but if Natsu is END then how come Natsu doesn't disappear more often in order to give Tartaros orders on what they should and should not be doing being the Guild Master and all.

Also when saying who will face Zeref again has me wondering if END has tried to fight Zeref in the past and obviously lose, inspiring him to use Face.