How often is Jeremy Maclin in the slot? Does LeSean McCoy always line up in the backfield? How often does Brent Celek pass block?

Those were the types of questions I answered in my debut InFocus article back in August. The study focused on a snap split comparison between 2011 and the previous two seasons. Here, I'm going to examine those snap splits through five weeks of the 2012 season.

Note: "Back" refers to any snap where the player lines up in the backfield. "Wide" refers to the split end and flanker position, or the outside receivers. "Slot" only counts snaps where the player is lined up in the slot. "IL" refers to snaps taken while lined up as an in-line tight end.

WR JEREMY MACLIN

Wide receiver Jeremy Maclin has already missed a game this season, but he's been a full-time player when active. As we can see in the above chart, there's not much to get excited about in terms of a change in role. Maclin is still working on the outside about 85 percent of the time, only dabbling in the slot a few times each game.

Considering that Maclin rarely pass blocks (three times in 50 career games) and is on the field for all but a few plays each game, the percentage of time he's blocking will always be nearly identical to the percent of run plays called when he's on the field.

Maclin has lined up to the left of Michael Vick 51 percent of the time this season and his 26 targets have been split evenly between the two sides of the field. The average depth of his targets when lined up to the left is just 11.8 yards, which is notably lower than his 16.2 mark when lined up to Vick's right. Not coincidentally, he's caught nine balls (69 percent) when on the left side and only five (38 percent) when to the right. This is trend that has picked right up where it left off in 2011. Plain and simple, Maclin generally works closer to the line when lined up on the left side of the field.

WR DeSEAN JACKSON

Similar to Maclin, wide receiver DeSean Jackson has seen similar splits between 2011 and 2012. After lining up in the backfield on just one of his 2011 snaps, Jackson has already done that on five occasions in 2012. He's been in the slot a tiny bit more, but nothing worth getting excited about.

One interesting item about Jackson so far this season is his production from the slot. Despite lining up inside on just 43 snaps this season, Jackson has run a route on 37 of those plays. He's been targeted six times, catching all six balls for 97 yards and his only touchdown on the year. Needless to say, teams should be keeping an eye on him (and expecting a pass) when he's in the slot.

Jackson's other 30 targets have been split evenly between 'wide left' and 'wide right,' which is exactly what we saw earlier with Maclin. Jackson's average depth of target is 15.6 yards when lined up to Vick's left and 22.9 when to his right. He's caught an impressive 13-of-15 (87 percent) balls from the left side, but only 4-of-15 (27 percent) when to the right. Again, this is very similar to what we saw with Maclin earlier. Vick is clearly struggling to complete passes to his star receivers when they're lined up wide to his right.

WR JASON AVANT

Jason Avant's splits are about the same as what we saw in 2011, with the only exception being a few extra snaps spent out wide; as opposed to his usual home in the slot.

Avant has lined up to Vick's left on 55 percent of his snaps this season, but seven of his 12 targets have come while on the right side of the formation. It's no secret (at least around Philadelphia) that Avant has excellent hands. It's shown in 2012, as he's hauled in 11 of those 12 targets.

Keeping with our trend of examining performance splits on the left and ride side, we'll see if Avant's production lines up with what we saw from Maclin and Jackson. The answer is that it does. The average depth of five targets to Avant while on the left side is 8.0 yards and he's caught all five balls. When on the right side, the average depth is 11.6.

WR DAMARIS JOHNSON

Wide receiver Damaris Johnson is worth a quick look because he played significant snaps while Maclin was injured and is now working as the No. 4 wideout.

Johnson has focused mainly on the outside, working in the slot only 11 percent of the time. This very much reflects the splits of 2011 No. 4 receiver, Riley Cooper.

Nine of Johnson's 13 targets have come while lined up wide right. He's hauled in six for 94 yards. The other four targets have resulted in two catches for 30 yards.

Note that, aside of a 55-snap effort in Week 3, Johnson has totaled just 42 snaps in the team's other four games, including nine total over the last two weeks.

TE BRENT CELEK

There's nothing overly interesting about tight end Brent Celek's snap splits so far this season. He's still spending about 85 percent of his snaps with his hand in the dirt, lining up as a wide receiver only 14 percent of the time. Celek plays a healthy chunk of the team's offensive snaps (92 percent to be exact), but you'll notice that he does come off the field more often in passing situations. He's missed eight run plays and 21 pass plays through five weeks.

Of Celek's 33 targets, 23 have come while lined up as in-line tight end. He's hauled in 16 of those passes and is averaging 14.0 yards per reception. When in slot or out wide, he's caught five of nine passes with a YPR of 22.0. Note that Celek is targeted by Vick a healthy 20 percent of the time when lined up as a wide receiver.

Of course, the stat everybody talks about with Celek is how often he's called on to pass block as a result of the team's rebuilt offensive line. The results show that he has, in fact, had to do more pass blocking than he's used to in 2012. Celek was asked to pass block between 23 and 25 percent of the time during three of the last four seasons. That mark was 15 percent during his breakout 2009 campaign.

In 2012, he sits at 29 percent, an increase of four percentage points over 2011. Doing some extrapolating, we're talking about a difference of near 20 pass routes on the year. That's 20 occasions where Vick has one less target on the field. That may not seem significant over a 16-game season, but it certainly limits what the offense is able to do.

TE CLAY HARBOR

Tight end Clay Harbor is worth a look considering that the team ranks 12th in the usage of two-plus tight end sets this season.

Harbor has been on the field for one-third of the team's offensive snaps this season. As we see in the above chart, the team has run the ball on 47 percent of those snaps. Harbor has been asked to block on 65 percent of his snaps, running just 41 pass routes on the year.

Similar to Celek, Harbor is being asked to pass block more often this season. On 350 snaps last season, Harbor stayed in to block 27 percent of the time. In 2012, that mark is up to 34 percent.

RB LeSEAN McCOY

Finally, we have the team's top offensive weapon, running back LeSean McCoy. "Shady" rarely lines up at wide receiver, spending about 95 percent of his snaps in the backfield.

Something that should really jump off the page here is the increase in blocking responsibility that McCoy has taken on this season. After being asked to stay in and pass block a career-high 136 times last season, McCoy is already about halfway to that point in 2012, with 67 through five weeks. Putting it into percentages, McCoy pass blocked 26 percent of the time when he was on the field and the team called a pass last season. That mark is up to 40 percent in 2012. Extrapolated the first five weeks over a full season, that's 76 occasions where McCoy will be asked to block, instead of running a pass route.

McCoy's targets are actually up so far this season, but it's been a result of Vick focusing on him more often when he actually does run a route. McCoy was targeted on 16 percent of his pass routes in 2011, but that mark is up to 24 percent in 2012. That rate will need to keep up or McCoy's targets will fall off dramatically.

We've seen here today that the Eagles offense has not changed much in terms of where players are lining up and what roles each is taking on. Unfortunately, we've also discovered a few explanations as to why the offense is struggling. The main one is the additional pass blocking being asked of Celek, Harbor and especially McCoy. Head coach Andy Reid has always prioritized maintaining a strong offensive line and this analysis shows us another reason why that's so important. Improvement from the line will be key a reason for the offense's success or failure going forward in 2012.

That's a wrap for this week. Keep an eye on the personnel packages this week against Detroit to see which are the most successful. Check out InFocus throughout the season for the most comprehensive Eagles analysis on the web.

Mike Clay, @MikeClayNFL on Twitter, is the Director and Managing Editor at Pro Football Focus Fantasy. He also works as an NFL Writer for NBC's Rotoworld.com.