User blog comment:IamJakuhoRaikoben/Chapter 515: I Am You... You Are Me, Review./@comment-112.202.164.133-20161221113732/@comment-28830364-20161221124814

Marin's magic made Erza unable to use her magic. Nothing to do with either of their power. Due to Marin, Ajeel got a good 5 minutes of free damage on to Erza. Which is why he gave her such a hard time.

If she used Nakagami from the start Ajeel would've been RIPed instantly.