For years, I was an unabashed Philip Rivers supporter. I had no preexisting affinity for the Chargers or Rivers, but in all the metrics I care about, Rivers was always one of the best. In 2008, 2009, and 2010, Philip Rivers led the league in yards per attempt. He finished first in ANY/A in ’08 and second in ’09 and ’10; he finished second in NY/A in ’08 and then first in NY/A in 2009 and 2010. Simply put, going into the 2011 season, no quarterback had been better over the last three years.

But Rivers regressed badly last year. Technically, his year-end numbers weren’t bad, thanks to a top-five finish in the final month, but Rivers ranked 17th in AY/A over the first 12 weeks of the season and clearly was a different player than the star he was the last three years.

This year, the bottom has fallen off. Before this weekend’s games, Rivers ranked 24th in NY/A and an unfathomable 29th in ANY/A; he also ranked 28th in yards per completion, particularly noteworthy for Rivers, who ranked in the top three in that metric in each year from ’08 to ’10.

So why Rivers is struggling?

In 2007, the Chargers did not draft an offensive lineman. They spent a 7th round pick on a tackle in ’08 and then drafted two guards in the third and fourth rounds in 2009. San Diego ignored the line entirely in 2010 and 2011, before selecting two interior lineman from the Big 10 in the 5th and 7th rounds of the 2012 Draft.

That’s a very long time to basically ignore five positions on your offense. All draft picks are not created equally, so I came up with a draft pick value chart based on the expected amount of Approximate Value for each pick. The table below shows how much draft equity each team has invested in their offensive line from 2007 to 2012:

Three weeks ago, Bill Barnwell wrote about how the Titans have completely ignored their offensive line the last several years; no argument from me here. The Jets are an interesting case because they selected Nick Mangold and D’Brickashaw Ferguson in the first round of the 2006 draft, so it’s understandable why New York chose to ignore the position for awhile. In addition, the Jets gave away a lot of draft picks during that time, so they haven’t had that many picks in general. From 2007 to 2012, New York made only 31 draft selections, the fewest in the league. But entering the 2007-2012 period, the Jets were set with two young lineman and Brandon Moore at right guard, limiting the need to spend additional picks on the line. On the other hand, some of the Jets’ offensive struggles the past two years are due to the fact that the team ignored the right tackle position and missed when drafting Vladimir Ducasse in the second round of 2010.

After the Jets and the Titans, no team has ignored the offensive line in the draft like San Diego. As a result, we shouldn’t be too surprised that the offensive line has deteriorated significantly over the years. Take a look at San Diego’s starting offensive linemen each year from 2006 to 2011 (with age in parentheses):

Pos	2006	2007	2008	2009	2010	2011
LT	Marcus McNeill (23)	Marcus McNeill (24)	Marcus McNeill (25)	Marcus McNeill (26)	Marcus McNeill (27)	Marcus McNeill (28)
LG	Kris Dielman (25)	Kris Dielman (26)	Kris Dielman (27)	Kris Dielman (28)	Kris Dielman (29)	Tyronne Green (25)
C	Nick Hardwick (25)	Nick Hardwick (26)	Nick Hardwick (27)	Scott Mruczkowski (27)	Nick Hardwick (29)	Nick Hardwick (30)
RG	Mike Goff (30)	Mike Goff (31)	Mike Goff (32)	Louis Vasquez (22)	Louis Vasquez (23)	Louis Vasquez (24)
RT	Shane Olivea (25)	Shane Olivea (26)	Jeromey Clary (25)	Jeromey Clary (26)	Jeromey Clary (27)	Jeromey Clary (28)

At left tackle, Marcus McNeill had a promising start to his career but retired due to injuries in August. San Diego struggled whenever McNeill wasn’t healthy, and added Jared Gaither off waivers late in the 2011 season. Unfortunately for San Diego, Gaither has missed much of the 2012 season due to injuries. In his place, undrafted rookie Mike Harris has been horrible, allowing 17 hurries, 3 hits and 2 sacks on 164 pass plays in the first six weeks, according to Pro Football Focus. Gaither was back against the Browns, although it didn’t appear to make much of a difference.

Kris Dielman was a mainstay at left guard until a concussion essentially ended his career in week 7 of the 2011 season. Remember the two mid-round picks used on guards in the 2009 draft? Tyronne Green, the fourth round selection from Auburn, has replaced Dielman at left guard while third rounder Louis Vasquez has played at right guard for the last four seasons. The Chargers should be happy to have drafted multiple year starters with those draft picks, but neither have otherwise outperformed their draft spot. Surrounded by strong tackles and centers, both guards would be capable members of a solid line, but the Chargers are not fortunate enough to be in that position.

Like the left tackle spot, the center position looked secure for a long time with Nick Hardwick after he made the Pro Bowl in 2006. But that was his only such honor, and he has steadily regressed since then. So far in 2012, Pro Football Focus ranked him as the 22nd best pass-blocking center. Right tackle has been an abomination for San Diego. Jeromey Clary was one of the worst starting tackles in the NFL last year, and the Chargers brought him back with similar results in 2012.

When healthy and at their best, Gaither and Dielman could help form a solid line, and Greene and Vasquez are not line killers. But unfortunately, San Diego has been without capable linemen for much of the last two years, and Rivers’ game has declined because of it. San Diego tried the penny-pinching approach to building an offensive line, and it hasn’t worked.

Breaking down Rivers’ passing stats

I believe that a quarterback can make his offensive line, as great quarterbacks can make pre-snap adjustments and post-snap reads to minimize the risk of a sack. However, Rivers was one of the more unique quarterbacks in the NFL from ’08 to ’10. According to target data from Footballguys.com, Rivers targeted his running backs far more than other quarterbacks during this period. He led the league in percentage of passes towards his running backs in 2008, and ranked in the top four in that category in 2009 and 2010.

Rivers may have targeted his running backs frequently, but he went down the field when he targeted his receivers. In 2008 and 2010, he led the league in yards per target when throwing at receivers, and ranked 2nd behind Drew Brees in that metric in 2009. Rivers also led the league in yards per target when throwing to his tight ends in 2009 and 2010. And he ranked in the top three in yards per target towards his running backs in ’08 and ’09.

Let’s not forget, in 2008 and 2009, he was throwing to LaDainian Tomlinson and Darren Sproles, and Sproles was still there in 2010. So his passes to running backs those years often went for big plays because of the talent around him, which no longer exists. His downfield throwing in ’08, ’09 and ’10 often went to Vincent Jackson and Malcom Floyd; the former is now in Tampa Bay, while the latter can’t make the passing game go by himself. Antonio Gates averaged 14.6 yards per catch in 2009 and 15.6 yards per catch in 2010; the last two years, he’s averaging just 12 yards per reception.

And while the talent has faded away, Rivers has had to adjust. While he threw a significant amount to his running backs from ’08 to ’10 – 27.5 % of his targets — that number was at 32% through seven weeks this year, and throwing to Ryan Mathews and Ronnie Brown aren’t making people forget about Tomlinson and Sproles. Against Cleveland, half of his completions were to running backs. He’s checking down more often partially due to a weak offensive line, and partially due to the lack of talent at wide receiver. Antonio Gates is struggling to get separation, catching just 21 of the 39 passes thrown his way, while Eddie Royal is soaking up passes and averaging just 4.3 yards per target. Of course, short passes to Royal are preferable to sacks, another way Rivers has had to adjust due to the lack of solid line play. And ex-Saint Robert Meachem has had little impact so far.

Rivers looks a lot worse now than he did two years ago, but it’s always difficult to separate the quarterback from the offense. He’s playing for a team that’s tried to build an offensive line in the cheapest way possible, and it’s starting to show. He’s lost two great running backs and watched his team replace them with a guy who can’t stay on the field and a guy who shouldn’t be on the field. His star tight end is showing the effects of age and numerous injuries over the last five years. And the receiver group is probably the least talented bunch he’s ever played with. I won’t rule out a Ken Anderson-like career rebound for Rivers in a couple of seasons, but from where I stand, San Diego needs upgrades on the offensive line, at wide receiver, and if Antonio Gates and Ryan Mathews can’t stay healthy, just about everywhere else.

Of course, despite being a Rivers supporter, I’m not blind the other side of the coin. He was an extremely fortunate quarterback to play with Tomlinson, Sproles, Gates, and Jackson, along with a solid offensive line. But when he had that, he was a dominant quarterback, which is exactly what a great quarterback should be when surrounded with good weapons.