Someone in the media (forget who) mentioned he was told by the Rams' staff that the OL might struggle a bit early on but they felt come the end of the season and playoffs the line could end up being better. That projection and gamble ended up being accurate early on, as they did struggle, and they didn't get to see whether they were right (that the guys they chose could get on a roll once they figure things out) due to injuries.
I tend to think they were wrong, that if Boom & Allen had stayed healthy both would have been replaced in the lineup. Boom was a huge dropoff in physicality and his pass pro did not make up for that. Allen was a huge dropoff in pass pro and his run game play did not make up for that.
Either way that doesn't mean neither of them have a future as starters. Just means they need to improve and this time around actually win jobs in camp if they want play time in 2020.
