After a phenomenal preseason by Sam Bradford and the gang, the Eagles looked like world-beaters. After four weeks playing games that matter, however, not so much. The following was a five-part series, consolidated into one post where you can grade each positional group on the Eagles' offense.

Sam Bradford

As a reminder, here's what the Eagles gave up for Sam Bradford back in March:

*Per Adam Schefter, the Eagles would have gotten a 3rd round pick if Bradford didn't play at all. They'll get a 4th round pick if he plays less than 50 percent of the Eagles' offensive snaps.

Bradford is also the highest paid player on the team, making $12,985,000 this season.

That trade isn't looking so hot at the moment. Bradford has simply been far from the accurate quarterback we saw in training camp and in the preseason, and he has the fourth-worst QBR in the NFL through four games.

On the "excuse" side, the running game hasn't helped, which always makes life more difficult on the quarterback, and his receivers haven't bailed him out by making difficult catches on balls that were off-target but reasonably catchable.

On the "non-excuse" side, with the exception of the Week 4 game against the Redskins, Bradford has had plenty of time to throw. The offensive line's struggles have come in the running game, not in pass protection. Bradford has mostly had very clean pockets to throw from, and he simply hasn't been able to put the ball where it needs to be.

Here are film breakdowns we did of Bradford in the Cowboys and Jets games:

     • Bradford vs the Cowboys
     • Bradford vs the Jets

Many of the throws in the above breakdowns should be lay-ups for a good, professional starting quarterback. They've been difficult for Bradford. The Eagles were hoping Bradford could bring stability to what has been a terribly unstable quarterback position since the Donovan McNabb days.

Below is a list of every team in the NFL, and how many quarterbacks they have started their respective team's opener since 2009:

See the teams above with at least four starting quarterbacks on opening day since 2009? Know how many playoff wins they have since the 2010 season, combined?

None.

If you listed the teams around the league who were likely to have someone different behind center in 2016, where would the Eagles be on that list?

Quarterback Grade: D

Running backs

Continuing on with our "quarter pole" grades, we'll turn to the running backs.

DeMarco Murray

Here are DeMarco Murray's numbers through four games this season with the Eagles, compared with where he was at four games into the 2014 season:

Obviously, he had better blocking in Dallas last year... No wait, let me rephrase that.

Obviously, he had blocking in Dallas last year. There. That's better. 

When Murray has had some room to run, he has shown glimpses of what he was a year ago. He had a 30 yard run against the Redskins that was reminiscent of 2014, and a 17-yarder against the Falcons that was called back because of a holding penalty. Otherwise, his rushing attempts have looked a lot like when the computer "picks the right play" against you in Tecmo Bowl:

The Eagles traded LeSean McCoy to the Bills for Kiko Alonso, and then signed Murray and Ryan Mathews, a pair of "downhill, north-south" runners to replace him. I'm not sure McCoy would be faring much better here with the way the Eagles' offensive line has run blocked, but certainly, the money the Eagles paid to their trio of running backs has not been an investment that has paid off so far.

Here's a look at what the Eagles are paying their running backs this year, via overthecap.com. They're third in the NFL:

In 2016, they'll be paying this trio over $17 million, which is currently by far and away the highest in the NFL:

Not to be a master of the obvious here, but Murray isn't going to be productive if the Eagles don't give him the football. Conversely, they can't just keep giving him the football if the offensive line is going to be a human turnstile.

It's just a really bad situation.

Ryan Mathews

Mathews is the Eagles' leading rusher, with 132 yards. That's 37th in the NFL. Like Murray, Mathews hasn't gotten many carries. On the season, he has just 33 of them, or an average of just over eight per game. Mathews was the "beneficiary" of better blocking against the Jets Week 3, which was where 108 of his 133 yards came from, although I wouldn't exactly say the Eagles' run blocking in that game was stellar.

While he has run hard, Mathews has had some crippling mistakes. He had an egregious drop against the Falcons Week 1 that would have gone for good yardage, and he dropped an imperfect but catchable pass against the Jets that might have gone for a touchdown. He has also lost two fumbles this season, one of which was at a time in the game against the Jets where the No. 1 thing he had to accomplish was securing the football.

Some have viewed Mathews as a bright spot this season. I have not. While he has provided a spark at times on what has been a dreadful offense, the egregious mistakes would be amplified in a "normal," productive offense.

Darren Sproles

Like Mathews, while Sproles has provided a spark at times, he has had some bad moments at key times during games. He had a drop that would have been a TD against the Jets, and was unable to bring in a pass he got both hands on in a huge third down situation against the Redskins (although to be fair, it was a poor throw from Sam Bradford). Sproles the return specialist has been great. Sproles the offensive weapon has been somewhat overrated thus far.

Overall running back grade: C-

To note, the running backs are tough to grade. Are we grading them on expectations? If so, this was a group that was regarded as the best RB trio in the NFL. Maybe a D or an F is in order. Is it fair to give them an incomplete, because the Eagles haven't really tried to run the ball due to a completely ineffective run-blocking offensive line? Or maybe you see positives that I don't. You decide...

Wide receiver

Onto the wide receivers:

Jordan Matthews

Matthews leads the Eagles' receivers in catches and yards, by a mile:

Nelson Agholor

Agholor is really tough to evaluate. At times, he has gotten open and Sam Bradford has simply missed him.

Like here:

And here:

And here:

As a result, his numbers look bad: 7 catches, 100 yards, 0 TD.

However, I won't make excuses for him on the fumble on the reverse the Eagles tried to run against Washington Week 4, which was an inexcusable error.

Agholor is talented, and I believe that if the offense was more efficient he could be thriving. But at the same time, you would like to see him bail out his quarterback on a few off-target throws, which he has not been able to do.

Riley Cooper

The best blocking wide receiver in the history of the NFL.

Miles Austin

Austin had a 39 yard TD reception against Washington that is fresh in everyone's minds, but it's been more bad than good when the Eagles have tried to get him involved. Against the Jets, the Eagles threw four times to Austin on third down, and completed none of them. Austin's fit on this team is odd. He's a reserve wide receiver who doesn't contribute positively on special teams. The Eagles paying him $2.2+ million this offseason still just makes no sense to me at all.

Josh Huff

A few times a game, we see Cooper tell Huff not to take a return out of the end zone, but otherwise he's been invisible.

Overall wide receiver grade: C-

Tight ends

Onto the tight ends:

Zach Ertz

Many were expecting Ertz to break out this season, especially early in camp when he dominated in practices. But then a sports hernia derailed his preseason, although he was able to return in time for the Week 1 game in Atlanta. Ertz's numbers are unimpressive.

Ertz's 104 receiving yards put him at 26th among tight ends. Only three of his 10 receptions have moved the chains. Worse, Ertz's 10 receptions have come on 19 targets (a bad percentage), one of which glanced off Ertz's hands and into the arms of a Dallas defender, which essentially sealed the game Week 2. It's difficult to say how much Ertz's injury has affected him so far, but clearly he is a player the Eagles need to step up and make some plays.

Brent Celek

Celek has not blocked well in the run game, and he has two receptions this season. We've posted this here numerous times, so apologies for the redundancy, but Celek's numbers have declined in each of the last four years.

Celek counts for $5 million against the cap next season. That is an unjustifiable figure.

Trey Burton

Burton is tied for fifth in the NFL in special teams tackles. Clearly, he's on the punt cover team.

Overall tight end grade: C-

Offensive line

During the offseason, the Eagles cut the oldest (Evan Mathis) and sixth-oldest (Todd Herremans) projected starting offensive linemen in the NFL, and they still had the oldest starting offensive line in the entire league heading into the season. That's what happens when you only draft one offensive lineman in three years, as the Eagles did.

By comparison, here's a chart of how many offensive linemen each team in the NFL has drafted over the last three years:

The NFL average during that span is 4.125 drafted offensive linemen per team. Because of their failure to add youth to the mix along their OL, the Eagles did not have much in the way of quality depth, either in terms of young developmental players or experienced, reasonably reliable veterans.

Herremans was clearly a declining player, so his release was understandable, but Mathis was still a quality starter, even if overrated by the likes of ProFootballFocus.com.

Allen Barbre was a 31-year-old journeyman with one career start since 2009, and just eight starts over the course of his career. He, of course, filled in at LG in place of Mathis. Andrew Gardner, meanwhile, was aging in his own right at 29, and was on his sixth team in the pros. He won Herremans' old starting job at RG in training camp and the preseason.

When you dump both guards in one offseason, you're simply not going to have any semblance of cohesion. 

• The LT will not be used to playing next to the LG. 

• The LG will not be used to playing next to the C. 

• The C will not be used to playing next to the RG. 

• And yes, finally, the RG will not be used to playing next to the RT.

It takes a long time for an offensive line to get good at blocking blitz pickups, stunts, twists, etc. The Eagles' offensive linemen hadn't logged a significant amount of time playing with the guys immediately to their left or right. That was a clear concern heading into the season, and it has shown on the field.

Gardner actually played reasonably well before being placed on IR with a foot injury. Barbre has simply not played well at all at LG. Unquestionably, the Eagles would be a better team with Mathis at LG instead of Barbre. As we detailed at length back in July, the Eagles handled the Mathis situation poorly. There's really no excuse whatsoever for the Eagles to have simply dumped him after not addressing the offensive line either in the draft or free agency. They thought Barbre would not be a significant dropoff. 

Obviously, that was a miscalculation. Or something.

Otherwise, heading into the season, there was reason for optimism at the other spots. During the offseason, I can remember suggesting that the Eagles might have the best LT-C-RT combo in the NFL in Jason Peters, Jason Kelce, and Lane Johnson. That statement sounds ridiculous now, as none of them have played up to expectations.

While the Eagles' OL has pass protected well (in the first three games, anyway), the run game has been an outright mess. The Eagles' rushing attack:

As we noted earlier today, the Eagles have been awful on third down, but that has been a product of the Eagles' complete inability to run on first down:

On first downs this season, by my unofficial count, the Eagles have called 43 designed run plays. Some facts about those run plays:

• They average 3.16 yards per carry on called first down run plays.

• Eight of those 43 called runs (almost one in five) went for negative yardage.

• 17 of those called runs (40 percent) went for 1 yard or less.

• Only 7 of those called runs (16 percent) gained more than 5 yards.

It's a vicious cycle. If you can't run the ball on first down, you won't convert on 2nd and 3rd down at a reasonable clip, and then you literally can't run the ball on first down because you just punted. I might add here that Donnie Jones is on pace to punt the ball 104 times this season. Only four punters have had more in a single season since 2006. 

If the Eagles cannot run the ball effectively, their offense is ruined. And the reality is, it could actually a lot worse with Peters and and Johnson both banged up.

Overall offensive line grade: D-

Follow Jimmy on Twitter: @JimmyKempski