Think Crawford will be fine. Today's medical technology, procedures and rehab protocols, all greatly help. He'll be missed for sure though. Greg Ellis returned after tearing his Achilles & won comeback player of the year, notching a career high 12.5 sacks. Barry Church looks good so far.
I'm one that really wishes they'd have signed Israel Idonije when they had the chance...both prior to and after the draft, and well before the injuries. I understand the team wanting to trend towards young players on the whole, and I certainly agree. But Idonije just made sense. He's familiar with Marinelli & the scheme, can play DE & DT, & 20.5 of his 28.5 career sacks came in the last 3 seasons with Marinelli as his DC, including 8 sacks in 2010 & 7.5 in 2012. The Boys likely would've had a leg up on signing him with Marinelli being with the team and he signed a very cap friendly 1-year $840,000 deal with the Lions.
I think Garrett has shown some things, but that doesn't mean he'll stay around if the team doesn't translate it into wins. Last season, the team continued to fight & scrap and had a chance to win the division, despite the worst rushing stats in franchise history, the OL being horrible, missing half of the starting D by the end of the season, the Brent/Brown situation...etc. The team didn't quit despite all of that. I think the dual roles of HC/OC was too much, and like the idea of Callahan calling plays. We'll see how it goes, but if things go badly, there's more to blame than just Garrett. Already, injuries & lack of depth on the D-Line are issues...as is bad O-Line play.