What Has Happened to the St. Louis Rams' Pass Rush?

After the St. Louis Rams graded out with the second-best pass rush in the NFL in 2013, per Pro Football Focus (subscription required), the team had the 18th-ranked unit heading into its Week 6 matchup against the San Francisco 49ers. 

Though the defense finished last season with 53 sacks, the third most in the league, it was dead last prior to Monday night's game, with just one recorded.

That lonely sack doesn't belong to All-Pro Robert Quinn, but rookie Aaron Donald, whom St. Louis drafted in the first round of the 2014 draft despite having arguably the league's most fearsome pass rush with Chris Long, Quinn, Michael Brockers, Kendall Langford and William Hayes, all of whom had at least five sacks in 2013. 

Quinn had five sacks through the first five games of the season last year on his way to 19. 

	Sacks	QB Hits	QB Hurries
2013	5	10	15
2014	0	6	6

Though head coach Jeff Fisher was optimistic the unit would improve Monday night against the San Francisco 49ers, in many ways its fall continued during the 31-17 loss.

Colin Kaepernick attempted 36 passes against St. Louis—far more than the 26.5 opponents were attempting against the Rams through their first four games of the season—and yet even with increased opportunities to bring pressure, Kaepernick walked away having taken zero sacks and little in the way of hits or hurries. 

Kaepernick's 120.5 passer rating was also significantly higher than the 98.5 average rating per game the Rams had allowed opposing quarterbacks previously this season.

As ESPN.com's Nick Wagoner pointed out after the loss to San Francisco, one sack in the first five games is the worst start in that category in NFL history. 

The decline of the Rams' pass rush this season has been nuanced, but perhaps the most glaring culprit is the ankle injury Long suffered in Week 1 that required surgery and will keep him out until November. It is the domino that has put undue stress on the other pieces around it. 

Opponents double-teaming Quinn in Long's absence has been the obvious culprit for the veteran's decreased production.

As Jim Thomas of the St. Louis Post-Dispatch astutely noted in one example this year, on the 23 passing plays for which Quinn was on the field against the Dallas Cowboys in Week 3, Quinn was double-teamed on six and triple-teamed on one, leading to zero sacks, quarterback hits or quarterback hurries in that game. 

To put that in perspective, in the 16 games in which he played last season, there was not a single one that Quinn didn't have at least one sack, hit or hurry, per Pro Football Focus.

Long only had two such games last season but generated 63 total pressures on the year, averaging out to 3.9 per game.

Some will point to the fact that the Rams have the No. 1-ranked passing defense, having allowed just 1,112 yards on the season through Week 6, as evidence that the less effective pass rush isn't necessarily hurting the defense's ability to stop the passing attack.

But in truth, opponents have attempted just 142 passes against the Rams so far in 2014, the fewest in the league. There are just fewer plays on which the Rams can try to bring pressure against the quarterback, and as long as they continue to give up 139.8 rushing yards per game, opponents will keep the pass attempts to a minimum. 

Still, the defensive front should be able to capitalize on the opportunities it is receiving to rush the passer. If Quinn is being double- or triple-teamed, theoretically that should free up Brockers, Langford, Donald, Eugene Sims or Hayes, all of whom can be used as pass-rushers to make plays on the quarterback. 

That's the question that continues to loom for St. Louis, a defense that has for so many seasons now prided itself on its versatility up front. 

L.G. Patterson/Associated Press

Brockers has been conspicuously quiet to start the season, with zero sacks, one hit and no hurries through the first five games, after recording two sacks, three hits and four hurries through the same period last year, per Pro Football Focus. 

It's been a similar story for Langford, who had one sack, one hit and four hurries through the first five games in 2013 but has just one hit and one hurry in 2014. 

Quinn and Donald, on the other hand, have shown an ability to win their matchups and record pressures—they combined for four hits and four hurries on Nick Foles in Week 5 against the Philadelphia Eagles—but the sacks remain elusive. 

"We're getting pressure on the passer," coach Jeff Fisher said Friday, via The Associated Press (h/t USA Today). "I think what we proved we were capable of over the last two years, teams go in and they game plan and the ball's coming out. We had plenty of hits and plenty of pressures last week (against Philadelphia), we just didn't get him down."

Until the Rams get Long back in November to help free up Quinn and get another elite pass-rusher back in their stable, they can improve the rush by improving the run defense.

If St. Louis can become stout there, teams will be forced to take to the air, creating more opportunities for disruption.