Seattle's offensive line has been bad. For stretches it's been okay, and for stretches it's been historically awful, but in general it has been bad. It's not exactly a surprise that the offensive line has been bad, as fans have had gripes about the offensive line for a few years now and entered this season looking to replace two starters. The drop off has been jarring though and, combined with the varied failings of the entire team, frustration among fans is beginning to boil over.

Enter Tom Cable.

Cable has been the offensive line and assistant head coach in Seattle since joining the team in 2011. He came to the Seahawks highly regarded for his work in the running game in his first five seasons in the NFL, which was impressive enough to land him a brief stint as a head coach in Oakland. It was a track record that, at the time, was a little dubious.

Cable's first year in the NFL was in 2006 as an offensive line coach in Atlanta under offensive coordinator Greg Knapp and head coach Jim Mora Jr. That season the Falcons were the number one rushing team in terms of total years, out-rushing the second place team by nearly 400 yards. In terms of DVOA, the 2006 Falcons ranked 5th overall in rushing offense.

It was a very impressive showing for a rookie offensive line coach, but it comes with some caveats. The NFL was still scrambling to figure out how to defend a quarterback like Michael Vick. Cable took over in Vick's 4th full year as a starter. With Vick at the helm the Falcons had finished 14th, 1st, and 1st in total rushing yards and 9th, 3rd, and 7th in rushing DVOA. Considering this previous success, it's difficult to evaluate Cable's individual contribution to that 2006 team.

Cable left Atlanta for Oakland the next season after the Falcons fired Jim Mora at the end of 2006. Here Cable was present with a significantly different situations. The Raiders had won 11 games the previous three years combined, and had finished 29th in both total rushing and rushing DVOA in the year before. Cable took advantage of the opportunity to make an immediate impact, resurrecting Robert Gallery's career with a move to guard and improving the team to 6th in total rushing yards and 19th in rushing DVOA.

These gains were quickly lost as the Raiders entered the Jamarcus Russell era. In 2008, Jamarcus played respectably for a first year quarterback but the rushing offense slipped to 10th in total yards and a miserable 31st in rushing DVOA. In 2009, Jamarcus fully melted down and the rushing offense slipped all the way to 21st in total yards and 26th in rushing DVOA. This is also Cable's first full season as head coach in Oakland.

To this point in his career, Cable had held course in one season with an established running game, seen encouraging improvement in his first year with a struggling franchise, and watched the wheels come off in his other two years. It's a mixed bag at best, but it's what he does after this point that earns Cable his reputation as a top notch offensive line coach.

2010 may be the best year of Cable's career. Oakland overhauled their offensive line, adding 3rd round pick Jared Veldheer at left tackle, returning Robert Gallery from injury at left guard, and promoting Langston Walker to starter at RT. Darren McFadden had his first, and so far only, healthy season behind the revamped Raiders offensive line and the team improved to 2nd in total rushing and 7th in rushing DVOA. Cable was with the Raiders for the acquisition of every player involved in their 2010 rushing attack, with the exception of Robert Gallery who he was directly involved in transition to guards.

Despite those improvements and snapping a streak of seven years with a losing record, Cable proved otherwise incapable of being a head coach and was fired after the 2010 season.

This brings us to his time as a Seahawk. Cable was brought in alongside offensive coordinator Darrell Bevell. While Bevell may have the coordinator title, Cable shares some of the responsibilities. Doug Baldwin once referred to Cable as the "run-game coordinator", and Cable's impact on the rushing game was fairly immediate. Seattle went from 31st in total rushing yards and 28th in rushing DVOA, to 21st in total yards and 14th in rushing DVOA in Cable's first season. Since then, Seattle has had a dominant rushing attack. The Seahawks have finished 3rd, 4th, and 1st in total rushing yards and 1st, 7th, and 1st in rushing DVOA. Even this season, with all of their struggles along the offensive line, Seattle was ranked 5th in total rushing yards and 9th in rushing DVOA as of last week.

Despite this steady run of success, the Seahawks offensive line has been eroding. In the table below, you can see how the Seattle offensive line has evolved over the Schneider, Carroll, Cable era. The new color in each row represents the new group of linemen Seattle added that season.

Seattle has retained five players from Cable's first season in Seattle, only two of which Cable was with the team when they were acquired (J.R. Sweezy and Alvin Bailey). Seattle attempted to invest in the offensive line starting in 2010, spending a first round pick on Russell Okung, and then again in 2011 spending a first round pick on James Carpenter and John Moffitt.

Since 2011, Seattle has spent a late second, two mid-rounders, and three late-round picks on the offensive line despite the turnover they've experienced in that group. It's unclear whether this is because of previous failures (Moffitt was underwhelming with off field concerns before being released, and Carpenter was not offered a 5th year option and then allowed to leave in free agency), or because Cable has wanted to take a different tact towards building his offensive line.

While player acquisition is generally the responsibility of a team's front office, Cable is believed to be highly involved in the process. John Schneider explained Cable's involvement like this:

"We're not going to draft a guy [Cable] doesn't like," Schneider said. "He doesn't have the final say, but we would never draft somebody he doesn't think could play. You are totally spinning your wheels there."

You don't have to look any further than Seattle's desire to convert athletic defensive linemen to the offensive side of the ball to see Cable's fingerprints on front office decisions. From Seahawks.com:

When Cal found itself thin at center, a young offensive line coach named Tom Cable convinced one of his team's freshmen defensive linemen to switch positions. Jeremy Newberry struggled a bit at first playing his new position—a season opener against San Diego State's La'Roi Glover, who would go on to become a six-time Pro Bowler—didn't make the conversion any easier for Newberry, but eventually he became one of college football's best centers and went on to a Pro Bowl career with the San Francisco 49ers. Later at Cal, Cable convinced defensive tackle Tarik Glenn to become offensive tackle Tarik Glenn, and the result was a 10-year career in Indianapolis that included three Pro Bowl selections and a Super Bowl ring. .... "This really started a long time ago," Cable said. "Doing this, it's a little bit nerve-wracking for a minute, and then once you convince them that if they'll just follow your direction and stay with it and don't get frustrated, it can happen. Of course J.R. has done it, and now Drew's done it, and Garry's done it from being a tight end. You've got Kristjan (Sokoli) doing it, (practice squad center Will) Pericak doing it.

Jesse Davis, Kona Schwenke, Kamalie Matthews, and Justin Renfrow can also be added to the list of defensive linemen that Seattle has taken a look at on the offensive line. The ultimate goal with these conversions is to get more athletic on the offensive line.

"I can go get a guy who runs a little faster, jumps a little higher and has an aggressive streak in him, and at least I can see that on defense, and I can start with him. I'm going to have to retrain an offensive lineman out of college anyway."

To date, this process has yielded one established starter in J.R. Sweezy. Outside of defensive line conversions, only Justin Britt has earned regular playing time. Bailey was expected to find a starting role on the offensive line after showing as a capable fill in the past two years, but disappointed in the preseason and returned to a backup role.

A major mitigating factor in some of the talent issues that Seattle has faced along the offensive line has been the discovery of the read option. While the rushing game's improvement to respectability from 2010 to 2011 can largely be attributed to Cable and his work with Marshawn Lynch especially, the jump from 2012's solid run game to the dominant rushing attack in 2013 and 2014 is in part due to the added dimension added by Russel Wilson's ability to rush for yards. Wilson's 849 rushing yards in 2014 was the 5th most by a quarterback since 1970, and ranked 17th in the NFL last year.

While it's certainly hard to say that Cable has not been successful at generating a run game, there are some valid questions about that success before taking into account the other half of an offense. There are a thousand more ins and outs that could be discussed around Tom Cable's ability to coach pass protection, but the high level view isn't kind. Cable's offensive lines have ranked 31st, 27th, 30th, 31st, 24th, 20th, 32nd, 24th, and 32nd in Football Outsiders' Adjusted Sack Rate. By regular sack%, Tom Cable quarterbacks have ranked 31st, 22nd, 32nd, 29th, 27th, 29th, 35th, 27th, and 34th (among qualified quarterbacks).

It is not completely fair to judge Cable on those numbers. The list of quarterbacks that played behind those offensive lines includes two mobile quarterbacks, prone to increase sack numbers, and Jamarcus Russell. There are, however, reasons to think that Cable's philosophies don't lend themselves to strong pass protecting units. On top of preferring raw offensive lineman, Cable puts a lot on the plates of his linemen.

"I think they have to [be interchangeable], We've always kind of double-trained guys, but I think we've all seen how it's paid off for us here, especially the last two years. Most of the time, it takes a little more effort, it takes a little more time from the coaches side because it's a bigger investment. You've got to do more, work more. And, then there's also the ego of the player, he'll say, ‘by god, I'm just a right guard, and that's all I'll be', and that's okay, they can go play for somebody else. They can come here, and that's one of the first things that we tell them, ‘we're going to ask you to do a couple of things.'"

Asking inexperienced players to train at multiple spots in a position group that demands precision footwork and technique is opening the door for mistakes. As Cable says, it's takes more from the coach to both teach the extra techniques and balance how much is being asked of the player. Whatever the reason, it's concerning that his offensive lines have never even approached average in any measurement of pass protection.

Tom Cable is a complicated case. On the surface, he's had an incredible run of success coordinating rushing attacks. When you dig deeper, however, you can find reasons to be concerned about what he really brings to an offense. Is the 2015 season an example of those concerns proving to be valid, or is putting together the 9th best rushing attack by DVOA (and 15th overall offense) with the talent he's been given a tribute to his abilities as an offensive line coach?