User blog comment:B214/Volume 23 discussion blog/@comment-31137559-20170412031517/@comment-49.177.99.124-20170412042328

Your over thinking it, Issei was the weakest because while he was a human he never even showed a hint that he had a SG, even Raynare took a while to confirm if he had one or not.

Even Ddraig said when he was finaly able to talk to Issei that he was to weak in the past that he couldn't talk to him.