PHILADELPHIA (973espn.com) - Back-to-back, top-five finishes in Chip Kelly's first two seasons as the Eagles head coach say his offense has been as advertised for the most part.

You can debate the value of raw numbers or dispute the efficacy of a high-volume offense but as far as yardage is concerned, Philadelphia piled it up at a breakneck pace whether Michael Vick, Nick Foles or Mark Sanchez was under center in 2013-14.

Through six games this season, it hasn't been quite as bad as advertised but Chip's offense has taken a significant step back, ranking 12th overall in the NFL at 353.8 yards per game.

Each individual aspect is ever lower than that with the embattled Sam Bradford-led passing game at No. 14 with 249.8 YPG, and the DeMarco Murray-fueled ground attack ranking 19th, compiling 104.0 YPG.

If this were politics you could spin the struggles on just about any aspect of the offense. The line was awful for the first month as the new guards struggled and the Jasons (Peters and Kelce) underachieved. Murray, meanwhile, has looked like the square peg being pounded into the round hole, Jordan Matthews is nowhere near being a true No. 1 receiver in this league, and Bradford has looked anything but comfortable running this system.

But, don't discount scheme issues also.

Opposing NFL defensive coordinators now have plenty of film to study Kelly's core philosophies and they have been burning the midnight oil, devising schemes to deal with the spread, zone-read looks that were popularized at the college level.

The philosophy Kelly brought from Oregon is designed to create spacing and when he arrived in Philadelphia, he already had an additional hurdle to overcome based on the actual field.

If you were watching college football on Saturday you know the hash marks are far wider at that level, something that allows the offensive line to split farther apart, sometimes even a yard away from each other. The NFL is far different and when you turn on the TV this Sunday notice the stacked line of scrimmage which almost naturally takes away some of that space Kelly craves.

The tempo aspect of Kelly's belief system is designed to limit substitutions and make the defense declare its intention early in the play clock, making a potential read far easier for the QB. That's the good, the bad is it also eliminates pre-snap adjustments and signal callers well-equipped to change things at the point of attack are inherently wasted in this offense.

Post-snap things are also designed to be "quarterback-proof," generally one-read and go, something that limits the difficulty of reading defenses but again hamstrings a signal caller who is capable of handling progressions.

Furthermore, in most spread offenses, 90-plus percent of the snaps are coming from the shotgun or the pistol, something that can decrease mechanical issues, at least when it comes to footwork. Those three-step, five-step and seven-step drops are a bigger deal than you think.

For the most part Chip has been running the same offense since Day 1 in Philadelphia, cataloging tendencies for others to exploit. That and a sharp decline in talent at the receiver position likely explains the drop off this season and it's time for Kelly to adjust to the adjustments made to him.

The truly great coaches at the professional level are not slaves to any system because they realize you are never going to have every piece in place to run a preferred look. That's not to say, you shouldn't strive to build toward your Valhalla but the special mentors assess the talent they have on hand and accentuate their strengths while masking as many deficiencies as possible.

Kelly has shown at least a few signs of being that guy this season by putting Bradford under center at times, something he has no real desire to do.

But, it's not enough.

A zone-read look is completely wasted on Bradford because even the most obtuse of defensive players aren't buying the fact he might keep it at the mesh point. Meanwhile, Murray looks about as comfortable in that offset-shotgun look as a Clinton who knows Congress is closing in.

And you name the QB ...Brady, Rodgers, Joe Montana and Otto Graham would all struggle at times if their top option was named Matthews.

The solution to all of this isn't simple but the answer is. If Chip the coach wants to keep running his system, Chip the GM better furnish him with better fits.

-John McMullen covers the Eagles and the NFL for 973ESPN.com. You can reach him at jmcmullen44@gmail.com or on Twitter @JFMcMullen