I came up with this thread in my sleep
We saw what Renji Bankai was able to do with First Ress Yammy and 17 months training will not do much to change that. Maybe he could make Yammy a little more angry.Didn't Renji become stronger during TS? I think he would be able to give at least some kind of a fight to someone who is weaker than pre TS Ken.
He def overstayed in the arrancar arc alone. He enters the stage around the same time as AA and is defeated shortly before Nnoitra. The top 3 wishes they got that much focus. But it doesn't end there.He sure does love his mad scientist tropes, but I never understood that particular one. Szayel's fine, not bad, he just way overstayed his welcome.