EAST RUTHERFORD, N.J.—The Giants' win over the Green Bay Packers last weekend didn't merely complete their return to relevance. It has set them up as one of the stories of the NFL season.
After dropping their first six games, the Giants have ripped off four straight wins, leaving them just one and a half games out of the NFC East lead, with a critical game against Dallas coming up. It counts a turnaround that no one saw coming.

Giants coach Tom Coughlin 
Well, almost no one. Back in October, after the Giants beat the Minnesota Vikings for their first win of the season, The Wall Street Journal laid out a 10-point plan outlining exactly how they could reach the playoffs.
Included on the list: running back Andre Brown coming back strong; the Giants beating the Eagles in Philadelphia; and the Cowboys succumbing to a monumental meltdown. (Alright, we didn't exactly need Nostradamus for that one.)
Since then, the season has unfolded precisely as we anticipated. But now that the Giants have climbed back into contention, we've got some bad news for this team and their revitalized fans: They aren't going to make the playoffs.
For reasons that range from a punishing slate of opponents to the precarious condition of key players, the Giants' turnaround appears doomed to fall short. Here are 10 reasons why this team will be sitting at home in January:
Tough sledding. To make up that one-and-a-half-game deficit in the NFC East, the Giants will have to overcome the toughest remaining schedule of any team in the division. Their remaining opponents have a combined .508 winning percentage, and none of their rivals face a slate of teams with combined winning record.
The starting receivers can't score. Hakeem Nicks hasn't scored a touchdown all season. Victor Cruz hasn't reached the end zone since Week 4 and said Wednesday that his salsa dance may soon appear on the back of milk cartons. The Giants have been able to cope by holding their last four opponents to an average of just 12 points a game. But their next six foes are some of the highest-scoring in the league, with a combined average of 25.8 points a game.
The knotty tiebreaker situation. The Giants didn't just dig themselves into a hole by dropping their first six games. By losing to the Eagles and Cowboys during that stretch, they contrived to fill the hole with quicksand. They have an inferior divisional record and stand to lose out on any tiebreakers in the event that they finish with the same record as Dallas and Philadelphia, who face each other in Week 17.
Jon Beason will break down. No one has played a bigger role in the team's turnaround than the linebacker, who arrived in a trade from Carolina early last month. But there's a reason the Giants were able to acquire a three-time Pro Bowler for a late-round draft pick: his health. Beason, who lost 27 games to injuries from 2011-12, has played 177 of the Giants' 179 defensive plays in the past three games. That looks unsustainable.
So will Andre Brown. The only player on the team with a longer injury history than Beason is Brown. He saw his rookie year ended by a torn Achilles, finished last season on injured reserve with a broken fibula, and missed the first nine weeks of this season after suffering the same injury in the preseason. In just two games back, Brown has already become the Giants' leading rusher this season, but his 48 carries raise questions about whether he can hold up.
The quarterback competition heats up. The Giants' four wins have come against Josh Freeman, Matt Barkley, Terrelle Pryor and someone called Scott Tolzien. But from here on out, they'll face a parade of prolific passers, including Matthew Stafford, Tony Romo and Robert Griffin III. And they're not the only quarterbacks the Giants have to worry about. With 16 touchdowns, no interceptions and a passer rating of 128.0 through six games, Nick Foles has turned the division-leading Eagles into an offensive juggernaut.
The abysmal AFC. Losers of three straight, the San Diego Chargers are now looking up at the Oakland Raiders in the AFC West. In other words, this team has no business being in the playoffs. But thanks to the general ineptitude of the AFC, the Chargers will be playing with playoff aspirations when they host the Giants on Dec. 8, rather than counting down the days until they can hit the beach.
Covering Calvin is a tall order. The Giants face the Lions on Dec. 22, which will present the team's improving defense with a big problem. Like, 6-foot-5 big. The Giants' defense will have to find a way to cover Calvin Johnson, the NFL's leading receiver, with a diminutive cornerback tandem of Prince Amukamara (6-feet) and Trumaine McBride (5-foot-9.)
Prime-time problems. The Giants have already been flexed out of the Sunday night slot once this season, so they welcomed this week's announcement that their NFC East matchup against the Redskins will remain in prime time. They shouldn't have. Though Eli Manning has a reputation for playing his best in big games, he has a win percentage of just .455 in prime-time games.
The Panthers' streak. The Panthers already roughed up the Giants in Week 3. But their red-hot winning streak counts as another blow. Were Carolina not in contention, Seattle could have all but locked up the NFC's No. 1 seed with a win over New Orleans next weekend. Now the Seahawks will likely still be fighting for homefield advantage when they face the Giants in Week 15. Which means more Russell Wilson and less Tarvaris Jackson at MetLife Stadium.
Write to Jonathan Clegg at jonathan.clegg@wsj.com