User blog comment:IamJakuhoRaikoben/Chapter 463: Black Carpet, Review./@comment-1359322-20151123093846/@comment-7418318-20151123101405

Maybe she meant that if Natsu was knocked out, Happy could grab him and carry him to savety thanks to his speed.

In that sense Happy can be usefull, even if it's just as a quick get-away.