How long does it take to build a 3-4 defense?

When the Bears announced the hire of defensive coordinator Vic Fangio, most fans were excited for the team to land such a sought-after, well-thought of defensive mind.

On the other hand, it seemed like a bit of a departure for new head coach John Fox, who comes from a strictly 4-3 defensive background to hire a coach rooted in the 3-4 scheme.

In his press conference last week, Fox brushed off this notion that he is married to one scheme over the other:

As for the defensive side, Fox said distinguishing between a 4-3 or 3-4 scheme is overrated in importance. But Fox's background is rooted predominantly in a 4-3 front, and the Bears are currently assembled as a 4-3 team.

"We're going to put our players in the best position for them to have success, and that's how we're going to earn their respect," he said.

While that sounds all good and proper, that was also before the hire of Fangio was even made, so it could have been Fox just keeping his cards close to his vest.

While it is likely that neither coach is tied to the scheme with which they are associated and instead use a hybrid front, it is interesting to consider the possibility of a full-time 3-4 defense in Chicago.

For starters, the Bears in their entire history have never utilized a base 3-4 defense. The other thing is that the talent they have in place has been curated for a 4-3 front going back to Lovie Smith's Tampa 2 and then Mel Tucker's...uh...scheme.

The Bears have only a few players who fit into a 3-4 front. Just browsing many of the threads since the Fangio hire was made, that considerable time has been spent debating how long it takes to implement an effective 3-4 unit. So I thought I would find some recent examples of teams that made the switch from 4-3 to 3-4 and see how much of a jump in rankings they made from the last season in a 4-3 to their first in a 3-4 and, when relevant, how much personnel turnover they had and how many seasons until the unit became formidable.

2008 to 2009 Green Bay Packers

2008 4-3 ranks: Points allowed - 22nd, yards allowed - 20th

2009 3-4 ranks: Points allowed - seventh, yards allowed - second

Returning starters: Eight

Spin: The Packers went from 6-10 and defensive coordinator Bob Sanders to 11-5 with Dom Capers manning the D. The biggest acquisition they made was Clay Matthews, who has ended up as a key part of their 3-4 attack. They also drafted B.J. Raji in '09, who didn't have a huge impact as a rookie (one start) but has been a key NT for Capers.

1999 to 2000 New England Patriots

1999 4-3 ranks: Points allowed - seventh, yards allowed - eighth

2000 3-4 ranks: Points allowed - 17th, yards allowed - 20th

Returning starters: Seven

Spin: There were some growing pains for Bill Belichick in converting from Pete Carroll's 4-3 to a 3-4. They finally hit their stride in 2001 when they jumped to sixth in points allowed (yet were 20th in yards allowed). They gained another three new starters for the 2001 season to help them get it going.

2012 to 2013 New Orleans Saints

2012 4-3 ranks: Points allowed - 31st, yards allowed - 32nd

2013 3-4 ranks: Points allowed - fourth, yards allowed - fourth

Returning starters: Five

Spin: This will be the one will be the one that Bears fans will look to to gain hope. The Bears have been hopelessly bad the past two years and this quick turnaround should give hope that the same can happen here. The Saints did do a lot of work in the draft (Kenny Vaccaro, John Jenkins) and free agency (Keenan Lewis, Parys Haralson) to aid the turnaround. The Saints also took a dive in 2014 (28th in points, 31st in yards) in their second year in a 3-4.

2013 to 2014 Tennessee Titans

2013 4-3 ranks: Points allowed - 16, yards allowed - 14th

2014 3-4 ranks: Points allowed - 29th, yards allowed - 27th

Returning starters: Six

Spin: Ray Horton, another noted defensive guru couldn't do much with the Titans unit he inherited last season as they saw a significant drop in rankings. This despite a good number of returning contributors.

2012 to 2013 Philadelphia Eagles

2012 4-3 ranks: Points allowed - 29th, yards allowed - 15th

2013 3-4 ranks: Points allowed - 17th, yards allowed - 29th

Returning starters: Four

Spin: Defensive guru Todd Bowles did not get much out of the unit, which started poorly under the much-maligned Juan Castillo in 2012. It's strange that their defensive rankings would invert but not improve much either way. The unit actually took another step back in 2014 (22nd points, 28th yards).

So overall it's kind of a mixed bag. There are other teams that have done these movements but I thought five was enough of a sample size. It seems that there is not a huge amount of hope for a quick turnaround, but with the right personnel and coaches it's possible. Well-known defensive coaches such as Rob Ryan and Dom Capers did better than others. Fangio is known for getting the most out of his group, which can give a lot of hope to fans.

Can Fangio coach up a unit that is lacking talent, or will it be a couple more years before the defensive returns to its Monsters presence?