3. Amon-Ra St. Brown suffers a major injury
Depth at wide receiver for the Lions is somewhat of a concern for the Lions, in particular light of Williams' six-game suspension to start the season. A move to add someone of some note could come at some point, before training camp or between the start of camp and Week 1.
St. Brown is the clear No. 1 target in the Detroit passing game. If he suffered a major injury, there's simply no replacing him--even in a trade if the timing fit to make such a move in reaction to his absence. He did miss one game and was limited by injuries in a couple others last season, but a longer absence this year would be a nightmare for the Lions.
2. The offensive line gets hampered by injuries
"Hope so. We didn’t have our projected starting offensive line for one game last year,” Decker said. “We had some guys come in and play great and give us some really good games -- or even if they had to go in for a series or two. But as we know, that’s the nature of this -- seems like for two years we’ve been trying to get this projected offensive line on the field together, and I don’t know if it’s happened yet. I don’t think it has. Preseason maybe.""
Depth behind Detroit's starting five offensive lineman--Decker, Jonah Jackson, Frank Ragnow, Halapoulivaati Vaitai, Penei Sewell--is broadly not great; as can be said for many teams. If Sewell, Decker or Ragnow in particular missed substantial time for the Lions, it would be massively bad. Ragnow's ongoing toe issue, which he of course fully intends to play through again, is notable.
Jared Goff needs great protection to function at his best, and any backup is a big drop-off to almost any starter on this front five. All five need to be together, ideally for every meaningful snap over all 17 games (and anything beyond) this season