How Important is Cortland Finnegan to the Rams’ Pass Defense?

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As the St Louis Rams gear up for Sunday's game against the Jacksonville Jaguars, they will have to take the field without Cortland Finnegan, who is nursing a hamstring injury. "Good," many fans will say, and point to his absurdly high passer rating against this season, or take the long view and point out his sad decline over the past year. It is assumed that the defense might benefit from his absence. And it might. 

But there is little reason to celebrate. Finnegan's play might be the single most important factor in the Rams' ability to shut down opposing quarterbacks. His decline — or his absence — may likewise handicap the Rams in a critical way. 

You would think that with Blaine Gabbert coming to town, the last of my worries would be "can we shut down the quarterback." But Jeff Fisher's Rams have a very checkered past with terrible passers. Witness the following:

Nov 18, 2012 – Mark Sanchez (Career 55.1% completion rate): Completes 75% of his passes in a 27-13 win.

Nov 25, 2012 – Ryan Lindley ("Career" 52% completion rate): Completes 60% of his passes in a 31-17 loss. 

Dec 9, 2012 – Ryan Fitzpatrick (Career 59% completion rate): Completes 75% of his passes in a 15-12 loss. 

Dec 16, 2012 – Christian Ponder (Career 59% completion rate): Completes 71% of his passes in a 36-22 win. 

If the Rams defense does its job against that quartet of terrible passers, the Rams win all four games instead of barely mustering a 2-2 split. That is the difference between a 7-8-1 season and a 9-6-1 season and a possible playoff berth. 

Of course, giving up a high completion percentage is not a big deal if you are limiting the damage done after the catch by the receivers. As Rams fans well know, a third down completion is useless if it doesn't move the ball past the sticks. That's why advanced statistics such as Football Outsiders' DYAR and ESPN's QBR take this into account. 

However, whether by traditional measures (such as the NFL quarterback rating) or advanced ones, the regression of the Rams' pass defense was evident. 

As the chart shows, the Rams were relatively successful in shutting down opposing quarterbacks in the first four or five weeks of the season, and relatively unsuccessful after that. In fact, the only quarterbacks that the Rams defended well after week 4 of the 2012 season — Kevin Kolb, Ryan Lindley (4 INTs), and Josh Freeman — are all now unemployed. 

So, what changed after week 5 of 2012? If you're looking for a tipping point, look at Pro Football Focus' player rating of Cortland Finnegan. 

Finnegan was Jeff Fisher's first marquee free agent signing in St Louis, and perhaps as much as any player is responsible for establishing Fisher's defensive tone on the field. (The two are also uncommonly close, with Finnegan reportedly renting a room in Fisher's house this offseason.) Early on, the signing paid dividends. 

Passer rating vs Finnegan: 2012 games 1-4: 33.5

Finnegan is always on the field, but when opponents line up a receiver in the slot, Finnegan will slide over to play that slot receiver. Where NFL's passing game used to revolve around elite outside targets such as Jerry Rice, Randy Moss or Terrell Owens, the modern NFL now puts enormous emphasis on that slot receiver. His job is to break defenses by finding holes in zones or making nearly undefendable sight reads on man coverage.

Finnegan excelled in the first quarter of the season in this job, reading quarterbacks and breaking on the ball, and able to come away with 3 interceptions and 6 more passes batted away. 

Passer rating vs Finnegan: 2012 games 5-16: 92.8

In weeks 7-8, Finnegan was tasked with defending two modern masters of the slot in Randall Cobb and Wes Welker. The two combined to catch 8 of 10 passes thrown with Finnegan in coverage as the Rams failed repeatedly to get the opposing offense off the field. 

This was a snapshot of a larger trend. After Week 5, Finnegan lost his knack for making plays on the ball, defending only two passes and failing to register an interception. Moreover, he missed 9 tackles over that span of games. Finnegan didn't show up on the official injury report until late November with a thigh bruise, but something was up.  

However, when the field got shorter, Finnegan regained his effectiveness. No touchdowns were charged to the slot CB for the entire season. 

Passer rating vs Finnegan: 2013 games 1-4: 158.3

With the Rams' pass defense now reaching historical levels of ineptitude, Finnegan's putrid play is receiving additional attention. Opposing quarterbacks have completed 16 of 19 passes thrown his way. He has yet to break up a pass or grab an interception, has three missed tackles to his name, and has already given up three touchdowns in coverage. (In his defense, one was after a blatant and uncalled offensive pass interference by Dez Bryant.)

Through Finnegan's troubles, Fisher has refused to call out his favorite player (or any specific player by name), and if he has contemplated benching him, hasn't made that thought public. Now, though, another leg injury appears to have made that decision for him. Finnegan was knocked out of Thursday's contest, and is listed as "doubtful" for this weekend's game. 

Per Jim Thomas, the Rams dealt with Finnegan's absence by giving Trumaine Johnson full-time reps outside, and moving safety Rodney McLeod into the box to defend slot receivers. 

If the Rams are going to avoid a repeat of the disastrous Mark Sanchez game, the Rams' defensive backs are going to have to make plays. Blaine Gabbert is far from a good quarterback, but he does have a strong arm and is being coached to release the ball as soon as he hits the back of his dropback. He does so whether the coverage is there or not. 

Quite simply, the coverage has to be there. Whether it's Finnegan, McLeod, or rookie Brandon McGee, someone has to step up.

The Rams defense doesn't lack for playmakers, but it has lacked an identity so far this season. You can point the finger at overmatched coordinator Tim Walton, but ultimately the players have to make plays.