User blog comment:B214/Volume 23 discussion blog/@comment-31137559-20170410043119/@comment-10330822-20170411014502

Yamcha fights too, he fought with the crew all the way up to the Buu Saga, which where he retires. He also isn't usually part of the main cast either.

But you are missing the point either way. Saji is comparing himself to Issei, even though like you said Issei is the furthest thing from the norm. That is just like how Yamcha compared himself to Goku and his friends despite most of them not even being human.

To "normal" people he is advanced, just like Saji is rather advanced, and, even though they aren't as advanced as a MC, they are still more advanced than many.

Either way, we are getting off-topic. The point is Yamcha and Saji are comparable because they were basically characters who were in the same position as the MC, but got left in the dust for whatever reason.