Thinking Defensively: Free Agency Impact on aFPA

Editor’s Note: We asked Anthony Stalter to give us a rundown of how teams were affected in free agency (and changes in coaching) on the defensive side of the ball. We used his suggestions along with our own observations to tweak 2013 Adjusted Fantasy Points Allowed (aFPA), which gives us a starting point for 2014 Strength of Schedule. We will tweak again after the NFL Draft if necessary. Below are Anthony’s thoughts on which defenses helped (and hurt) themselves the most this spring.

Run Defense Upgrades

▲Atlanta Falcons
The additions of DT Paul Soliai and DE Tyson Jackson should significantly improve a defense that allowed 135.8 yards on the ground a year ago. The Falcons have relied on smaller, quicker DTs throughout Mike Smith's tenure in Atlanta, but GM Thomas Dimitroff made it a point of emphasis this offseason to get bigger and tougher up front. He overspent, but this is one of the more improved run defenses on paper.

▲Chicago Bears
The Bears allowed 5.34 yards per carry last season so all they can do is go up. Free agent addition DE Lamarr Houston is criminally underrated and versatile, capable of lining up as a defensive end, defensive tackle or outside linebacker depending on the front. DE Willie Young was also a solid addition to the front four from both a pass-rushing and run-defense standpoint.

▲Tampa Bay Bucs
Free agent addition DE Michael Johnson was actually more effective versus the run last year than he was as a pass rusher. Thus, lining him up alongside DT Gerald McCoy and in the same front seven as LB Lavonte David should help a run defense that was average a year ago. Now that Lovie Smith has taken over as head coach, he'll also put an emphasis on turnovers, which will help the defense as a whole.

▲Minnesota Vikings
Hiring the defensive-minded Mike Zimmer will help overall, but I really liked the addition of DT Linval Joseph and re-signing DE Everson Griffen was a plus as well. I don't know if they're in for a dramatic improvement but the Vikings will be improved nonetheless.

Run Defense Downgrades

▼Kansas City Chiefs
I don't think the Chiefs are in store for a massive downturn but losing DE Tyson Jackson hurt. Along with NT Dontari Poe, he was one of their best run defenders in 2013.

▼San Francisco 49ers
The 49ers are going to be fine as long as MLB Patrick Willis mans the middle of their defense and NT Glenn Dorsey doesn't take a step back after a productive 2013 campaign. But LB NaVorro Bowman is expected to start the season on the PUP list after suffering that gruesome knee injury in the NFC title game, S Donte Whitner signed with the Browns in the offseason and who knows what OLB Aldon Smith's status will be like from week to week. Plus, at some point all of these extra games over the past few years will catch up to the Niners. I think their defense may fall off a cliff at some point.

Pass Defense Upgrades

▲New England Patriots
The Patriots might be the owners of the most improved defensive backfields in the league after adding CBs Darrelle Revis and Brandon Browner. Losing Aqib Talib hurts, but not when you can replace him with Revis, who will likely shadow opponents' No. 1 receiver. Unlike Greg Schiano, Bill Belichick will use Revis' skill set to maximize his defense. I'm sure Belichick will also use Browner's size and physicality to the Patriots' benefit.

▲Denver Broncos
One of the Broncos' biggest needs this offseason was at cornerback, so the team signed former Bucs and Patriots Aqib Talib to a massive contract. Talib, coupled with the addition of safety T.J. Ward and edge rusher DeMarcus Ware, as well as a healthy Von Miller, will go a long way towards improving a Denver secondary that ranked 27th in the NFL in passing yards allowed a season ago. (The Broncos are also likely to add a corner early in the draft, too.)

▲NY Giants
It would be a misconception to say that the Giants' secondary played poorly in 2013 - they didn't. But signing CB Dominique Rodgers-Cromartie, CB Walter Thurmond and S Quintin Demps in free agency improved their depth and versatility.

▲New Orleans Saints
Seattle still owns the best safety tandem in the league but New Orleans is now as solid No. 2 after signing Jairus Byrd to a massive six-year, $54 million deal. Fellow safety Kenny Vaccaro made an impact as a rookie last year in Rob Ryan's defense and he should only improve playing alongside Byrd. Plus, by thwarting Atlanta's attempts to steal restricted free agent safety Rafael Bush this offseason, Vaccaro can now play the slot if Ryan wants to continue to use three safeties in nickel situations. The Saints still need to add a pass rusher via the draft but they nabbed the best safety on the free agent market in Byrd.

▲Jacksonville Jaguars
The Jaguars recorded the fewest amount of sacks (31) last season, so the addition of former Seattle defensive ends Red Bryant and Chris Clemons should improve their pass rush, which in turn should improve their pass defense. At least that's the hope.

▲Green Bay Packers
The jury is still out on whether or not DE Julius Peppers is a fit for Dom Capers' defense but Ted Thompson knows what he's doing (I've learned my lesson questioning him). If DE Datone Jones ever taps into his ability, then the addition of Peppers coupled with the maturation of Jones could be a huge plus for Green Bay's pass rush, which in turn helps the secondary.

Pass Defense Downgrades

▼Buffalo Bills
Losing S Jairus Byrd on the back end of their defense was a massive blow. They're likely to replace him with a rookie.

▼Dallas Cowboys
Because of Jerry Jones' previous mistakes with the cap, the Cowboys couldn't afford to keep Des Jason Hatcher and DeMarcus Ware in their front seven. Jones did add DT Henry Melton and kept DE Anthony Spencer but both players are coming off knee surgery so who knows how reliable they'll be. I don't know if they'll be able to get a consistent pass rush without Ware, which will hurt their secondary.

Pass Defense: The Jury is Out

St. Louis Rams
The Rams have an outstanding pass rush but they have no depth at corner and they need a true centerfielder to run Gregg Williams' scheme. Depending on what they do in the draft, they could actually jump to the "Helped their Pass Defense" category. We'll just have to wait and see.

Atlanta Falcons
As for the Falcons, cutting S Thomas DeCoud wasn't the problem. The problem is that they didn't do anything to address one of the worst pass rushes in the NFL. If they can land multiple impact players in the draft then they could be dangerous but that's a big "if."