The story was reported by ESPN's NFC South blogger, Pat Yasinskas, and this is actually good news for the Falcons and their fans.
While many people, myself included, assumed that Nolan would bring a 3-4 scheme into Atlanta and restructure the Falcons' defense, it is better that they are staying with the 4-3. The Falcons have been building a talented roster for a 4-3 defense for a few years now, and it may actually hurt them more than help them if they made the switch now.
Young linebackers Curtis Lofton and Sean Weatherspoon excelled in the 4-3 scheme this year, and the Falcons also have gotten a lot from defensive end John Abraham in recent years. If the Falcons made a switch now, then it could affect the play of these guys.
A popular example supporting this argument is middle linebacker Jonathan Vilma. He was drafted by the New York Jets and played very well in his first few years in the league. However, when the Jets made a switch from the 4-3 scheme to a 3-4, Vilma began to struggle and his play dropped immediately.
It could be difficult young players like Lofton and Weatherspoon to adjust to a 3-4 because of the differences in the systems.
The fact that the Falcons are staying in a 4-3 helps their defensive line as well. In 2011, defensive ends Abraham and Ray Edwards underperformed at times anyway, and taking away a defensive tackle and adding more to these guys' plates may not be the best move. The Falcons are also not sure if they would have had a good nose tackle in Jonathan Babineaux or any of the other current defensive tackles.
Sticking with the 4-3 scheme was a great move from Nolan, Mike Smith and entire Falcons' coaching staff.
I am sure that every Falcons fan was excited to see a drastic change in a defense that has never been elite, but Nolan will still affect Atlanta's defense in a very positive way. Nolan can be expected to get improvements out of this defense almost immediately, especially because there will be no change in the scheme.
If Nolan and the Falcons made the switch to a 3-4, then it could have slowed progression in many of their young defensive playmakers. However, by keeping the 4-3, it reassures the Falcons that they still have the right guys in place.
This may have disappointed some people, but the move is smart, and Nolan will still get results from this defense.