For discussion:
I think it is fair to say that Mannion has not looked good in preseason football.
I think it is also fair to say that Mannion has been playing with backups behind a backup line, which is not an entirely clear way to judge.
Let's say for argument that the Rams do not trade for or pick up another QB prior to the season.
Should the Rams get large leads in regular season games, do you give Mannion snaps to get live action with the 1's versus a real team, and find out for sure whether we really have a backup, also protecting Goff in the process?
Or do you keep him on the bench, even in blowaway games?