Manning and Co. have regressed for one or more reasons, but either way the production for each has dropped, and it's had a negative impact on all teams involved.
While injuries can play a part in regression, so can new schemes, locations and simply a reduction in talent. In the following slides we'll examine several players who have seen their production drop noticeably this season and attempt to figure out why.
Let's take a look.
In 2011 Reggie Bush had finally solidified his status as a starting NFL running back. The Miami Dolphins gave him the majority of the handoffs and he made the most of them by posting his first 1,000-yard season.
Bush has not been as impressive in 2012, having only mustered only 791 yards and five touchdowns in 13 games. He's averaging 4.4 yards per carry, which isn't horrible—except when compared to his impressive 5.0 yards per carry in 2011.
While he hasn't received as many carries this season, Bush has clearly regressed. He's part of an inefficient offense led by a rookie quarterback in Ryan Tannehill.
The Dolphins needed Bush to be in his 2011 form, but he's failed. At one point Bush was even benched this year, which is all that really needs to be said about his 2012 campaign.
LeSean McCoy of the Philadelphia Eagles has had a strange few seasons. Last year he managed over 1,300 yards on the ground and scored a ridiculous 17 touchdowns.
This season McCoy has had to battle injuries and simply hasn't been as productive. He's only appeared in 10 games and put up 750 yards and only two touchdowns.
It's a far cry from what most are used to seeing from McCoy, but his regression makes sense. McCoy plays on one of the worst teams in the NFL and has almost no talent around him. Quarterback Michael Vick has been hurt (and could make a pretty good case for this list as well), which means the team has gone with third-round rookie Nick Foles.
McCoy has had his injury woes, but when he's been fully healthy he has regressed massively.
Minnesota Vikings defensive end Jared Allen is one of the most prolific defenders in the NFL, but he's had a disappointing season considering the expectations placed on him coming into the year.
In 2011 Allen notched a jaw-dropping 22 sacks, which put him in line with some of the all-time greats. He accomplished the feat in 16 games while compiling 66 total tackles.
Allen has participated in 13 games so far this year, and he's regressed in a rather impressive manner. He has just nine sacks and 41 tackles.
Minnesota is one of the NFL's nice surprises, as the team is still in the hunt for the postseason, but Allen hasn't been a big part of that thanks to his continued regression.
Jason Babin has had a horrendous couple of seasons, not to mention what the last few weeks have brought him.
Babin was released from the Philadelphia Eagles because he had regressed so rapidly, but still managed to find a home with the Jacksonville Jaguars.
In 2011 Babin was one of the NFL's best as he notched 18 sacks with the Eagles. He followed that up with just five sacks this year in 11 games with the Eagles and was subsequently released.
After landing with the Jaguars, Babin has been just as mediocre, having only recorded one sack in two appearances.
It's hard to tell where Babin has gone wrong, but it's been enough for him to lose his job once already.
At one point, Nnamdi Asomugha was the best cornerback in the entire NFL as a member of the Oakland Raiders.
Then Asomugha landed with the Philadelphia Eagles.
Asomugha has now spent two seasons with Philadelphia, with neither of them being rather impressive. The 2012 season hasn't been kind to Asomugha as the season winds down.
Opposing quarterbacks have been picking on Aso, which is not something you typically see. He's defended just 11 passes and notched only one interception.
Most of the blame for Aso's continued regression can be placed on the defensive scheme he now plays in with the Eagles. Add in a coaching staff that has had multiple firings this season alone and it's easy to see why Aso is no longer anything more than an average cornerback.
Carolina Panthers quarterback Cam Newton has defined the sophomore slump. He posted historic numbers in his rookie year last season, but has regressed mightily in 2012.
In his rookie year Newton passed for over 4,000 yards, threw 21 touchdowns and added over 700 yards rushing along with 14 more touchdowns.
The sophomore campaign has been horrible to Newton. Carolina has been horrible, as has Newton, who has only thrown for just over 3,000 yards and 16 interceptions. He's also only rushed for over 600 yards and seven touchdowns.
The problem is simple to diagnose for Newton—NFL defenses have figured him out. He must now become a better pocket passer or he could be out of a job in a few seasons.
As a quarterback who plays in New York and has already won two Super Bowls—more than his famous older brother—Eli Manning is going to be placed under a massive microscope each season.
For that reason alone, Manning has regressed this season.
Last year, the younger Manning threw for just over 5,000 yards and threw 29 touchdowns and 16 interceptions, giving him an outstanding 92.9 quarterback rating.
Things have taken a turn for the worse for Manning in 2012. He's thrown for just 3,429 yards, 20 touchdowns and 13 interceptions. The numbers give him just a 86.4 quarterback rating.
Furthermore, the Giants have been struggling as of late, and are now in danger of losing their grip on the top spot in the NFC East heading into the postseason. Much of the blame can fall on the shoulders of Manning, who has regressed from his outstanding 2011 season.