User blog comment:Perchan/Fairy Tail 295 - In Which Sting Gets Less Douchey (Sting and Lector)/@comment-4566819-20120817174854

It is a risky move on natsu's part but if he uses both dragon forces and Thunder dragon mode, he could quickly over power both Sting and Rouge in a hurry, perhaps he was doing it to protect gajeel as stupid as it sounds in case of a overload of power.