by Derrik Klassen

Football is a game of attrition. The team left standing at the end of the year is not necessarily the best team, but merely the best team that remained healthy enough to compete.

For the Seattle Seahawks, injuries have derailed a defensive unit known to be dominant. Defensive end Cliff Avril was the first domino to fall in October. Seahawks defenders have gone down one after another since then, ultimately leading to the hobbled unit that allowed 42 points in a loss to the Los Angeles Rams this week.

In addition to Avril, defensive backs Richard Sherman and Kam Chancellor were inactive. Linebacker K.J. Wright also sat out after suffering a concussion last week. Finally, middle linebacker Bobby Wagner played despite battling a hamstring injury that forced an early departure from last week's game. Slowing down an explosive Rams offense with a battered defense was not going to be an easy task.

Speed was noticeably lacking from Seattle's defense. Since the dawn of the Pete Carroll era, Seattle's defense has prided itself on being faster across the board than their opponent. Wagner and Wright are one of the timeliest and most athletic linebacker duos in the league, and with Chancellor in the box, it was as if Seattle always had three All-Pro linebackers on the field at once. That dynamic was gone this week, and Rams running back Todd Gurley took full advantage.

The Rams are running split zone -- a zone run with a kick-out blocker who crosses the formation to block the back-side edge defender. With eight defenders in the box versus seven immediate blockers, the Seahawks should be able to comfortably fill every gap (in blue). Gap control was not the problem for Seattle on this one, though.

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Wagner is able to get to the line of scrimmage uncontested. Nine times out of ten, Wagner secures this tackle in the backfield without any trouble. Wagner with a nagging hamstring injury, however, does not have the twitch to keep up with Gurley. Gurley makes a daring dash parallel to the line of scrimmage to get to the perimeter, leaving Wagner in his wake. Once out in space, Gurley makes two more defenders miss before ultimately being shoved out of bounds after a 9-yard gain.

Seattle also battled with the structure of their defense. When the unit is healthy, Chancellor can fit into the box as an edge defender or off-ball linebacker. Chancellor can allow the Seahawks to get into under/over fronts and load the box as if they had three real linebackers on the field. With Chancellor next to Wagner and Wright, a healthy Seahawks defense has the most terrifying and versatile second-level defense in football. In the absence of Chancellor, Wright, and a healthy Wagner, however, the Seahawks are playing a style of football that does not fit the personnel.

When Chancellor is playing on the edge, he is inclined to attack the blocker full force and generate chaos at the line of scrimmage. The chaos is built into the structure of the defense with an athletic linebacker corps and a dominant, rangy free safety in Earl Thomas. There is faith that someone will fight through the chaos and clean up the mess. That was not the case on Sunday.

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Bradley McDougald (30) is playing in place of Chancellor. Normally, Chancellor would crash the line of scrimmage. McDougald, on the other hand, barely engages with the blocker and tries to shimmy his way through the inside shoulder. Without resetting the line of scrimmage, McDougald allows Gurley enough space to shuffle along tight to the line. Gurley does not have to commit early, making the read and pursuit angles trickier for the cornerback and linebacker. Terence Garvin (52), in place of Wright, is unable to react to Gurley fast enough and catch him on the boundary. Gurley slips the cornerback and blazes past Garvin for another nice gain.

Gurley continued to beat the Seahawks defense to the perimeter all day. Often by choice, Gurley was carrying the ball outside the numbers and prancing up the sideline for chunk gains. The Seahawks did not have the speed to keep up with Gurley.

The dagger came right before halftime. Down 27-0, the Seahawks finally strung together what appeared to be a respectable defensive drive. A 2-yard run and a strip sack that lost 12 yards put the Rams in a third-and-20 on their own 43-yard line with under a minute to go in the half. There was no reason for the upcoming play to result in anything other than a fourth-and-whatever to bring the game to halftime.

The Seahawks lined up in a conservative zone shell. On third-and-20 with halftime around the corner, any team would do the same. The issue is that the Seahawks defense did not have the speed to cover the field properly from such a spread-out alignment.

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It is built into the defensive design that Gurley will make it past the line of scrimmage. With 20 yards to go before the first down, the idea is that someone should catch him before he crosses the sticks. Instead, nobody even got a hand on him. Wagner takes an aggressive angle and fails to recover. Thomas gets tossed aside by left guard Rodger Saffold. McDougald, the theoretical last line of defense, also takes a tight angle and can not redirect to catch Gurley in space. Gurley weaved through the entire Seahawks defense untouched for a 57-yard touchdown run. The Rams went into halftime with a 34-0 lead, vaporizing any shred of hope that the Seahawks had of mounting a comeback.

The eye-test was not kind to Seattle. Gurley simply looked faster than his opponents every time he touched the ball. Even Thomas, the best free safety in football, struggled to do anything in the run game other than force Gurley out of bounds 10 yards down the field. Their run defense DVOA against the Rams was 9.2%, their second-worst single-game performance of the year. This comes on the heels of 30-24 loss to Jacksonville that was the team's third-worst run defense DVOA of the year. Only a Week 2 slog versus the San Francisco 49ers tops Seattle's past two weeks of disaster. (Subscription required)

Next week's game versus the Cowboys is a make-or-break contest for Seattle. Cowboys running back Ezekiel Elliott will make his return after serving a six-game suspension just in time to ravage a brittle Seahawks run defense. Fortunately, Wright has cleared concussion protocol and will be back in the lineup, but he alone may not be enough. Wagner, McDougald, and the defensive line must all play better. If the Seahawks defense lets Elliott run rampant the way Gurley did, their season may come to a heart-crushing close.