The only rationale for keeping Bortles is this, IMO:

Say he returns to 2017 form with the offense bailing him out and he minimizing his game losing/win preventing plays.

Great. They beat the odds for a year, sell tickets, and maybe whatever rookie they drafted is 100% ready and the franchise moves onward and continues upward in 2020 without him as QB1.

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Blake stays on and we get a repeat of 2018. Rookie isn't ready, either isn't played or the play doesn't make much difference because there's still too much to fix on offense.

They just tanked it (purposefully or not) and get an even better QB in 2020.

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Those are the only "good" reasons for keeping him on, IMO.

I still see them cutting him after June 1 (if they don't somehow, someway unload him first like Gabbert) to give more room to upcoming critical re-signings.

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