I see inside linebacker as a huge problem. I think edge rusher is a potential problem, as is safety. DL will be a problem too if Robinson has continued heart problems and can't get into proper shape. He didn't do anything in the games he played in last year as it is if I remember correctly. Joe Noteboom also can't be counted on as he's missed chunks of playing time every year he's been in the league.
This reminds me of two years ago when the Rams tried to start the year with Brian Allen as a starter at center and he was completely overmatched and overwhelmed.