Ultimately, Rob Ryan was a failure with the Dallas Cowboys.
The wealth of defensive talent in St. Louis made the opening quite attractive for Ryan, but he certainly doesn't guarantee anything.
Let's look at the best- and worst-case scenarios for the Rams defense in 2013.
The defensive line trio of Chris Long and Robert Quinn and the underrated William Hayes combined for 29 quarterback takedowns, while tackle Michael Brockers totaled four sacks of his own in his rookie campaign.
With the amount of front seven talent Ryan will have at his disposal, it's not unfathomable that St. Louis reaches the 60-sack plateau in 2013.
Long is in the prime of his career, Quinn will be entering his third year as a professional and Hayes will only be 28. Add in the ever-improving Jo-Lonn Dunbar and blitzing safety Quintin Mikell, and it's easy to see the Rams adding to their 2012 sack total with Ryan as the defensive coordinator next season.
As alluded to in the previous slide, the collection of talent along St. Louis' defensive front seven will keep the Rams among the league leaders in sacks.
However, dropping from 52 quarterback takedowns to 38 would be a drastic slide, and would represent the worst-case scenario in the first year with Rob Ryan as defensive coordinator.
He dealt with a variety of injuries in 2012, and the Cowboys only mustered 34 sacks. With a more healthy unit in 2011, Ryan's group accumulated 42 sacks.
The average of those two figures?
You guessed it—it's 38.
Just a round number on which to settle.
In 2012, the Rams surrendered 21.8 points per game (14th in the NFL) and finished 17th in points allowed per drive, per Football Outsiders.
Under Ryan, nearly a four-point decrease is the best-case scenario.
The core of the defense is set to return, and with an even more aggressive nature, St. Louis will not be an easy team to move and score the football against in 2013.
The Cowboys gave up 25 points per game and ended 2012 26th in points allowed per drive.
In 2011, they allowed 22 points per game and finished 19th in points surrendered per drive.
This worst-case scenario seems like a stretch, but Ryan's assertive defenses sometimes get burned and get gashed for huge gainers and plenty of points.
With the free-agent acquisition of Cortland Finnegan and the draft addition of Janoris Jenkins, the Rams fielded one of the league's most intimidating and continually pesky cornerback tandems last season.
After a year of playing together that tandem should be even more opportunistic.
As a team, St. Louis intercepted 17 passes, which tied for 11th in the NFL.
With a strikingly similar cornerback duo in Dallas, the Cowboys picked off only seven passes, the fewest in the league.
Hopefully for the Rams, the sheer talent in the defensive backfield will add around five more interceptions in 2013.
Dallas' low interception total should worry some Rams fans, but much of that had to do with the lack of a consistent pass rush.
If the injury bug hits St. Louis or opposing offenses throw a variety of quick passes at the Rams next year, there's a chance the team's interception total will dip significantly under Ryan.