I don't think we're going to see Keenum playing bad.
We'll simply see Keenum being Keenum, game in and game out; he does what he does, and can't do what he can't do. He's not going to escape a rush with quick movement or his legs, for instance. And he won't win games with his arm. He'll manage games and get the ball out quickly. This is unlikely to change, and Fisher knows it.

So that's why I think it has more to do with putting enough points on the scoreboard, not turning it over, and winning games comes after that.
If Keenum consistently moves the team, he continues to start. It's if we start seeing games that the Rams just can't score that we'll see Goff come in. But I maintain it wouldn't happen until the bye week. Keenum is not Foles. Keenum is much more consistent game to game.