I'm struggling to see any positives of Turner being out for the guts of this season. He's light years ahead of Foskey right now. It may be good for Foskey's development to be involved, but for the team as a whole, this is a negative. Whether Foskey develops and how quickly are question marks whereas Turner was a bona fide contributor to a strong rotation. While it's too early to definitively evaluate Foskey, I'm comfortable in saying that barely holding your own against mediocre, back up LT's is not a recipe to success against starting LT's, certainly not in the timeframe of this next 10 games.
So yes, this is bad.