If I were forced to choose one to sit, and I mean FORCED, it would be DeCastro. He's been dinged up pretty for three of the first four games and may need the rest to heal as much as possible. Dotson has played decently (better than expected) in his place. But, putting Hassenauer in for Pouncey and expecting him to make the line calls, etc., kinda scares me.
That said, I hope they are both able to give it a go this week. As long as it's "playing hurt, not injured". If they're truly injured, have to go with the next man up mantra and get it done anyway.