I've always felt John Clayon is the best journalist covering the NFL. Here's a great article on how Tony Dungy has changed the NFL with his Cover 2 defense.
Thirteen of the 25 teams playing 4-3 defenses made moves to acquire weakside linebackers this offseason. Much of the change relates to the popularity of Tony Dungy's Cover 2 defense, which asks for more speed and playmaking ability from defenders. The entire NFC North, which features three new head coaches, is going to the Cover 2 to keep up with Bears coach Lovie Smith, a Dungy disciple while an assistant at Tampa Bay.
I'm interested to hear WCG's and Sean Yuille's comments on this. The Bears and Colts had two of the best defenses in football last year. I believe they were ranked #1 and #2 respectively in points allowed. The Lions are now switching to the Cover 2. Bear coach Lovie Smith and Lions coach Ron Marinelli are both Dungy protege's from Tampa Bay. Marinelli was Dungy's d-line coach, and Smith was the linebacker coach.
Teams are also copying the Colts offense. The Bengals have based their offense on the Colts scheme, and even the Patriots started running offensive sets similar to Indy's last year.
This is indeed a copycat league.