How is he a below AVG backup? I am no expert, but in 2020 he played as an above average starter at RT, that is why Beane paid him 8M AAV. His play was worse in 2021 apparently, but do you really think he is below AVG backup? That doesn't make sense to me given the quality of OL play in the league.
Like I said I am not happy if backup OL takes 10M from cap space but since OL is a priority imo I'd save the money elsewhere (if they don't manage to keep him for less, which I hope they do). I am saying don't cut him unless you have better player then him.
And again, I have spent hours playing with our salary cap. We can save money elsewhere.