EAST RUTHERFORD, N.J. -- If you look at the surface statistics, Eli Manning is off to a strong start this season. There is a career-best 71.7 completion percentage, 1,381 passing yards with six touchdown passes and three interceptions through five games.

The New York Giants' starting quarterback seems fine heading into Thursday night's matchup against the defending Super Bowl champion Philadelphia Eagles (8:20 p.m. ET, Fox). He appears to be the same reliable quarterback he has been most of his career.

It’s underneath the wrapping paper, bows and bubble wrap where you realize there's little worthwhile inside. All those standard statistics are a hollow shell of numbers leading to losses.

Manning is 32nd in the NFL with an average of 10.31 yards per completion. He's 27th with a touchdown on 3.2 percent of his pass attempts. His 7.02 air yards per attempt put him 29th among quarterbacks.

“All you have to do is watch him,” one NFL executive said. “Don’t think about what his name is. Just watch him. Don’t make excuses. It’s blatant and obvious.”

These stats simply would be numbers if the Giants (1-4) were winning. But Manning is declining, and the losses are piling up.

His offensive line might be contributing, but there is nobody else left to blame. The Giants changed coaches, schemes and general managers, loaded up on weapons and invested heavily in a left tackle and a pair of guards in an attempt to prop up their quarterback. It's not working.

Behind closed doors, several Giants players have expressed frustration with Manning's performance, according to sources. One player specifically commented recently about Manning’s inability to do anything against Cover 2 and zone defenses.

Manning's struggles aren't really new, and can't all be pawned off on his offensive line. They're an extension of the previous two seasons, when the Giants were among the league’s lowest-scoring teams. This isn’t a five-game outlier. This has become the norm.

Consider:

• Manning was hit on 6 percent of his throws last season; now, he is near the middle of the pack in QB contact and 12th in pressure faced.

• Manning is holding on to the ball longer this year (2.65 seconds compared to 2.35 seconds in 2017) while playing in a new offense under coach Pat Shurmur.

• Manning has been sacked the fourth-most times in the NFL this season. He has also been sacked on 16 of 24 quarterback hits (67 percent), according to ESPN Stats & Information. Back in his second Super Bowl season (2011), Manning was sacked on just 46 percent of quarterback hits.

• The Giants are 23rd in points per game, despite having offensive weapons such as Odell Beckham Jr., Saquon Barkley, Sterling Shepard and Evan Engram, when he's healthy.

• They’ve failed to score 20 points in three of five games and reached 30 points on Sunday for the first time since Tom Coughlin was the coach in 2015 (Week 17).

• Manning has fewer touchdown passes (six) than all but two quarterbacks (Dak Prescott and Case Keenum) who have started five games.

• The Giants rank 23rd in points per game this season (20.8) and ranked 31st last season (15.4). They’re 34-52 over the past five seasons and have lost 18 of their past 22 overall.

When looking at why teams struggle in the NFL, start with the quarterback.

How did this once-proud franchise and quarterback get here?

The slow and painful decline

This is Manning’s 15th season as the Giants' starting quarterback. He’s a two-time Super Bowl MVP with a Hall of Fame-caliber résumé. But somewhere in recent years, there has been a significant drop-off.

It's as if the game changed on Manning, a traditional pocket passer who has become obsolete. In today's NFL, if you're unable to move around the pocket and avoid the wave of pass-rushers, it's almost impossible to be successful. Under pressure, Manning has 132 yards passing and no touchdowns on 48 dropbacks this season.

The second Manning or the Giants are off-schedule on an offensive play, it's as if the offense is dead. That limits them to quick-timing passes or puts them at the mercy of their wide receivers winning immediately at the line of scrimmage. That is a difficult way to exist in today's NFL, which is built on explosive offenses.

But don’t tell Manning he’s playing poorly or deteriorating.

“I feel good. I feel like I can play at a high level,” Manning told ESPN last week. “I can make all the throws and play this game at a high level and lead this team.”

This season was supposed to be different for Manning. Dave Gettleman, a Manning-friendly face, was hired as general manager. At his introductory news conference, he appeared sold that Manning had plenty left in the tank based on (in part) one of the only games he had seen from start to finish -- against Philadelphia -- up to that point.

Gettleman and the Giants built their offseason plan around Manning. It was a curious decision, considering the organization was fresh off a 3-13 season that included internal tumult. Three players were suspended for their conduct. The roster was overhauled; only 20 of the 53 players heading into Thursday night's game finished last season with the Giants.

The draft in April was flush with intriguing quarterbacks at the top. Four went in the top 10, but the Giants selected Barkley No. 2 overall, adding him to an arsenal that had Beckham, Shepard and Engram. All are first- or second-round picks taken over the past five years. The Giants drafted Richmond quarterback Kyle Lauletta in the fourth round.

“They made a mistake in the direction they chose,” an executive with an NFC team said at the time. He viewed it as the football equivalent of Pat Riley building the Miami Heat around Dwyane Wade right now.

It could be argued that the Giants have the best skill-position players in the league. They even overhauled the offensive line, signing former Patriots tackle Nate Solder to a four-year, $62 million deal with a guarantee of $34.8 million. There weren't supposed to be any more excuses for Manning.

The Giants' coaching staff has remained publicly supportive of Manning. Shurmur has objected to any idea that his quarterback is declining or playing poorly. But the rhetoric around the league seems to indicate that there has been a slip in his play. Jacksonville’s Jalen Ramsey wasn’t complimentary of Manning this summer, though he isn't complimentary of most quarterbacks. Dallas’ DeMarcus Lawrence took to social media to celebrate the fact that Manning was returning for another season. The Saints left with a victory in Week 4, then claimed they put a scare into the Giants' quarterback.

💰 Day for a lot of youngsters out there! @NFL Draft day! Here's to the @Giants NOT drafting a QB. #ILikeEli #KeepEli. pic.twitter.com/QlM25Nur9p

— DeMarcus Lawrence (@TankLawrence) April 26, 2018

Manning's top wide receiver seemed to imply that there might be a problem.

"I don't know," Beckham said when asked during an interview with ESPN's Josina Anderson if there is an issue at quarterback. "Like I said, I feel like he's not going to get out the pocket. He's not -- we know Eli's not running it. But is it a matter of time issue? Can he still throw it? Yeah, but it's been pretty safe, and it's been, you know ... cool catching shallow [routes] and trying to take it to the house. But I'm, you know, I want to go over the top of somebody."

The previous regime admitted that Manning was nearing the end. General manager Jerry Reese said Manning was on the “back nine” of his career before the start of last season. In recent years, some individuals inside the organization have believed that Manning is holding the team back. Most have since been fired.

Some thought Manning was the problem as far back as four or five years ago, according to sources with knowledge of the Giants’ thinking. Maybe they were right. It hasn’t gotten much better since, with 2015 being the outlier, when Manning got comfortable in the second year of Ben McAdoo's offense.

"All you have to do is watch him. Don't think about what his name is. Just watch him. Don't make excuses. It's blatant and obvious." anonymous NFL executive

If Manning and the Giants continue at their current pace, the frustration will intensify. It was palpable against the Saints when Manning overshot Beckham on several throws and didn’t target him on several others when he was running free. Beckham noted in his interview with ESPN that his discontent with the offense's effectiveness had been bubbling since a Week 2 loss in Dallas.

“Players watch the tape,” another source said. “They know the deal.”

Manning counts $22.2 million against this year’s salary cap. That will rise to $23.3 million next season if he remains on the roster for the final year of his current deal. The Giants have a $6.2 million dead-money decision to make -- that’s how much will still remain on their cap next season if they decide to cut Manning.

That kind of money wouldn't really put the front office in an untenable position, but as we've seen already, it's hard to say goodbye to a legend.

He’s back, but for how long?

Manning's benching -- or his decision to decline the previous regime's offer to start games before coming out in favor of Geno Smith and eventually Davis Webb last December -- looked to be the beginning of the end. He was being minimized, and the team had a high draft pick to find his successor.

But everything turned when the fans revolted against the plan of Manning sitting in favor of Smith before Webb was ready to start. Smith was the so-called “sacrificial lamb,” according to a source with knowledge of the decision. He could handle the inevitable onslaught that would come with the decision. As it turned out, Giants ownership could not.

The previous regime thought ownership was on board with setting the life-after-Manning plan in motion. Co-owner John Mara knew in advance of the intentions, down to the last detail. But everything changed when the plan was met with push-back from the quarterback and fans and the extended Giants family.

Ownership flipped the plan on its side in part because of a protest planned by former Giants for the following week at MetLife Stadium against the Dallas Cowboys, combined with the fans' outrage. McAdoo and Reese were fired, and Manning was reinstated as the starter under interim coach Steve Spagnuolo for the final four weeks.

The original move was made with the intention of getting Webb some playing time down the stretch. That never happened. Now Manning is the starter with no succession plan in place.

The losses, the visual evidence and the extended struggle to score points over a multiyear span have made defending Manning challenging for even his staunchest supporters. The heat is officially on the aging quarterback.

“So what else is new?” Mara said recently.

But this is unlike anything Manning and the Giants have seen. Manning turns 38 in January, the same age Dan Marino, Joe Montana and Steve Young were when they played their final seasons. Maybe he isn't on the same level as the indomitable Tom Brady and Drew Brees.

“He is toast,” former NFL offensive lineman and current ESPN analyst Damien Woody said recently.

He later added: “When you talk about Eli Manning and that Giants offense, he needs the perfect storm. He needs everything, the environment, perfect. He needs the protection to be perfect. He has the weapons. He has the running back. He has all those things. But that is not the nature of the National Football League. There are going to be times when you need to make plays off-platform, off-schedule. That is what the really good quarterbacks do.”

Manning hasn’t been able to do that for several years. The result? The Giants had a six-game skid in 2013, lost seven straight in 2014, dropped six of seven to end 2015, had a pair of five-game skids last season and are off to a rough start this season. That doesn’t happen to upper-echelon quarterbacks playing at a high level, no matter what is surrounding them. The Eli Manning who won a Super Bowl almost seven years ago is a thing of the past.

More than likely, the erosion of Eli Manning has been happening for several years. It has been there right before our eyes and is just now being brought to the surface.