If the Lions lose:
With a Lions loss, they drop to 6-3, while the Bears jump up to the same record. The first tie-breaker is head-to-head, which is null as both teams would have won a game against each other.
Here's what the wild card race would look like (remember, the top two teams make the playoffs):
1. Bears (6-3)
2. Lions (6-3)
3. Falcons (6-3 or 5-4) - vs. Saints next week
4. Cowboys (5-4 or 4-5) - vs. Bills
5. Buccaneers (5-4 or 4-5) - vs. Texans
If the Falcons win against the Saints, they would jump the Lions as they have the head-to-head tiebreaker, and the Lions would no longer control their own destiny. The Cowboys and Bucs could inch closer, but the Lions have the tie-breaker on both of those teams, so they'd still be a couple games back. Playoffs would still certainly be in reach, but they'd have to pull out some big games to keep either the Bears or Falcons at bay.
If the Lions win:
Oh man, the possibilities if we win. With the Eagles losing on Monday night, there isn't a clear threat in the NFC East to catch the Lions. The NFC West is terrible so the 49ers will win the division and aren't a wild card threat. The only real remaining threat would be the Falcons and Bucs in the NFC South and the Bears. It may be tough to stay above the Falcons, since they have the tie-breaker, but the Lions have the tie-breaker against the Bucs. Since there are two wild card spots, things would be looking awfully good.
1. Lions (7-2)
2. Falcons (6-3 or 5-4)
3. Bears (5-4)
4. Cowboys (5-4 or 4-5)
5. Bucs (5-4 or 4-5)
6. Eagles/Redskins (4-5 or 3-6)
So if you look closely, the Lions would have a three-game cushion over every wild card contender outside of the Falcons. They would hold the tie-breaker over the Bears, Cowboys and Bucs, so even if all three teams are 5-4 (only two games back), the Lions would actually be three games ahead with the tie-breaker. The remaining threats (Eagles and Redskins) will still be three games back, even if they win next week. There is no head-to-head tie-breaker decided between them and the Lions as they do not play each other this season.
So there's a huge difference here. Either the Lions are potentially on the outside looking in, or sitting pretty with a three-game lead for a playoff spot with seven games left in the season. The Lions must come out on Sunday with a sense of urgency, because this game will have a huge affect on the remainder of the season.