The Baltimore Ravens' defense has ranked among the NFL's best in each of the last two seasons, but the unit still underwent some significant changes in the offseason.

Former defensive coordinator Mike Nolan took the head coaching job in San Francisco, and defensive line coach Rex Ryan was promoted to coordinator. Ryan, the son of former NFL coach Buddy Ryan, scrapped Nolan's 3-4 formation in favor of a 4-3 scheme and the "46" defense that his father popularized in the 1980s. In the basic "46" formation, two defensive ends, a nose tackle, two linebackers and a "rush backer" line up along the line of scrimmage. The middle linebacker and strong safety line up a few yards back and form the second line of defense.

"To come into camp and have my defensive coordinator say you won't be touched, I feel like a kid all over again," linebacker Ray Lewis said during minicamp in June.

Good cornerbacks allow the "46" defense to excel, and that's exactly what the Ravens have in Chris McAlister, Deion Sanders and onetime Pro Bowler Samari Rolle (free agent acquisition).

Quarterback Kyle Boller is under pressure this season to prove he's not a bust. The Ravens' passing offense has ranked 32nd and 31st in Boller's first two seasons, respectively. With free agent wide receiver Derrick Mason (Tennessee) and first-round pick Mark Clayton (Oklahoma), a lack of talent at receiver can no longer be cited for the team's passing woes.

Ravens quarterback Kyle Boller can't afford to take a step back this season, especially after being given talented receivers with whom to work.