Hard to say how this changes from last week: winning is good, struggling on the road is expected against better teams but a sign of trouble against weaker teams. (Compare with the Tampa Bay game.)
First we look at Massey's predictions:
Week 4: at Dallas, slight favorite
Week 5: Chicago, favorite
Week 6: San Francisco, heavy favorite
Week 7: Atlanta, heavy favorite
Week 8: at Denver, favorite
Week 9: bye
Week 10: at Chicago, slight underdog
Week 11: Carolina, overwhelming favorite
Week 12: Green Bay, slight underdog
Week 13: at New Orleans, underdog
Week 14: Minnesota, heavy favorite
Week 15: at Oakland, tossup
Week 16: San Diego, heavy favorite
Week 17: at Green Bay, heavy underdog
Tossups are 50%; slight favorites are up to 3-2 (60%), then favorites up to 3-1 (75%), then heavy favorites up to 86% (5-1), then overwhelming favorites. Reverse for underdogs.
So you can see Detroit is favored to an extent in the rest of their pre-bye games and underdogs in half of their remaining games. Their Expected Wins are 10.95: this would give them the first wild-card spot (with Green Bay winning the division). It's not unreasonable to suggest that Detroit could be 8-0 at the break; a pessimist would suggest 5-3, losing both road games plus one of Chicago/Atlanta. Overall, best-case is probably 14-2 if everything goes right; a pessimist would say 8-8.
Football Outsiders isn't showing defense-adjusted data this early in the season, but their Playoff Odds report gives Detroit 10.5 mean wins, an 81.8% shot at the playoffs, 39.5% for a division title, 24.3% for the #1 seed, 17.0% for a Super Bowl appearance, and 7.8% for a Super Bowl victory. (Also, interestingly, 0.6% for going 15-1, the second-best chance behind Green Bay.)
The way the Lions are playing, I would lean toward 12-4, with an "upset" win at Chicago and a loss in the tossup at Oakland. I don't think they beat Green Bay either place ... they need to demonstrate that they can play a great game against someone better than the Chiefs first.
Obviously all these pretty much guarantee a playoff spot (with apologies to Braves and Red Sox fans). The issue will be the Green Bay games: lose those and the division title is out of the question, and any Super Bowl hopes will rest on at least one outdoor win. Split, and the Lions could get lucky; sweep, and it's hard to picture the Lions with anything less than a bye. (We know the NFC West winner will be playing in the first round; that leaves the East and South. A Lions team that sweeps the Packers would likely be 13-3 at worst.)
On the other end, the Chicago and Atlanta games are key to a playoff appearance. You have to hold serve. (The San Francisco game, too: you can't lose to "non-contenders".) 5 or 6 wins at the break would have sounded great prior to the season, but the way things are going, that could mean a 9-win season and no playoffs. Atlanta could turn things around (especially with a win in Detroit), Tampa Bay hasn't lost since the Lions game, and the NFC East could always produce two or three 10-win teams.
Current mood: optimistic