User blog comment:IamJakuhoRaikoben/Chapter 458: Morning Star, Review./@comment-1776824-20151026035039/@comment-3290324-20151026035958

As I already mentioned, the laws of regular humans don't really apply as much to Mages because they're endurance, durability, etc. are far greater and they literally have Magic flowing through them. In addition to this, Erza has shown more durability than anyone in the series to date. Her durability and endurance are perhaps her two greatest traits so I'm not surprised at all that she was able to land that finishing blow on him.

As far as her being out of commission though, I doubt it. I'm sure she'll be out of commission for a while, but Erza's a main character and is always one of the main fighters. If her only contribution to this arc was a fight that took up maybe around two chapters total, there'd be a lot of angry fanboys and girls. Myself included. :P