One of the most interesting developments in the first two weeks of the season involves the use of an eighth defender at the line of scrimmage.
This strategy has been employed for many years. The plan is for a safety or another defender to move close to the line, usually giving the defense extra resources to stop the run or pressure the quarterback.
What is interesting about the first two weeks of the season is how this concept is being used, and what it says about the quarterbacks currently starting in the league. The primary mission is to stop the run. Coaches are willing to sacrifice a big play or two to throttle an opponent's running attack. To place the safety near the line of scrimmage means playing more man coverage, a risky strategy if the quarterback is good enough to make big plays down the field.
But 19 of the league's 32 starting quarterbacks are younger than 30, and many are still in their formative years. Defensive coordinators are simply willing to challenge these quarterbacks to beat them, and the strategy is paying off so far.
One of the most fascinating showdowns came in the opener between the Bears and the Chargers. Chicago coach Lovie Smith used safety Adam Archuleta like a fourth linebacker against Philip Rivers. He stacked four defensive linemen up front and four defenders behind them.
Rivers, who ran a hot offense that scored 30.8 points a game in 2006, struggled against this defense. Having so many defenders at the line of scrimmage makes it hard for a quarterback to find a rhythm.
This season, his second as a starter, he's struggling against the pressure. Against the Bears, who shut out the Chargers for almost three quarters, Rivers leaned on two things -- handoffs to LaDainian Tomlinson and short passes to a surrounded Antonio Gates. Things got so out of whack, the Chargers had a stretch in which the ball went to fullback Lorenzo Neal on five of seven plays.
Rivers has struggled with the blitz, but it's not as if teams are putting an all-out assault on him. According to Stats, Inc., Rivers has completed 10 of 15 passes against the blitz for 68 yards. He's been sacked twice and intercepted once against the blitz. If Rivers can't go downfield against stacked defenses, that's a victory for opponents.
The wildest eight-man concept came in the Raiders-Broncos game Sunday. The Raiders used a three-receiver set against the Broncos, but that didn't stop defensive coordinator Jim Bates from putting eight men up at the line of scrimmage at times, leaving three defenders covering three receivers man-to-man.
Peyton Manning or Tom Brady would live for a couple of plays like that. Manning motions his hands endlessly at the line of scrimmage to draw that extra defender away from Marvin Harrison or Reggie Wayne. Imagine if a defensive coordinator would give him that without him having to motion?
The idea was to get in the face of Raiders quarterback Josh McCown and confuse him. While McCown rallied against more conventional defenses later in the game, he didn't beat the eight in the box. Consequently, he could expect more of that in the weeks ahead.
Most teams wouldn't think of taking these risks against Brady or Manning. It's bad enough when they try to blitz these two guys. Brady is a staggering 20-for-23 for 293 yards and two touchdowns against the blitz through two games. Manning is 6-for-10 for 97 yards against the blitz.
The great influx of talented safeties has also made the strategy more appealing. From Ed Reed to Troy Polamalu to Bob Sanders, there are so many good safeties with mobility and tremendous hitting ability.
The Colts tried an interesting strategy against Vince Young last week. Young has now replaced Michael Vick as the quarterback who scares opponents the most with his running skills. With a good offensive line and depth at running back, the Titans should also replace the Falcons as the league's No. 1 rushing team.
At times Sunday, Sanders became the eighth man in the tackle box, but he had a couple of duties beyond stopping the run. He could use his speed to blitz Young, and he could also spy his every move and try to get him after Young went through his reads downfield.
"We knew they were going to run the ball in certain situations," Sanders said. "My thing was to line up and stop the run. For the most part, I think we did that. We gave them a little bit more than we wanted to, but we got the win, so that is the most important."
With Sanders near the line of scrimmage, the Colts, known last season for their inability to stop the run, held running backs LenDale White and Chris Brown to less than 100 combined rushing yards. Sanders was also in position to contain Young when he tucked the ball under his arm and ran.
As a result of this defensive strategy, Sanders was the best defender on the field last week. He had 11 tackles and 2.5 sacks. For a safety known for playing in a simple Cover 2 defense, those numbers are incredible. Dungy and his coaching staff deserve a lot of credit for coming up with a neat way to stop a running quarterback.
"We were trying to keep him inside," Dungy said. "The times he did get out around on the outside, that hurts us."
Still, having Sanders as a fourth linebacker on such plays provided enough spacing on defense to give the Colts a chance to stop Young when he broke to the outside. Watch for more teams to try this tactic, although most of those teams won't have a safety as talented as Sanders.
The quarterbacks who struggle against the blitz are usually the main targets, including Minnesota's Tarvaris Jackson, Atlanta's Joey Harrington and San Francisco's Alex Smith.
It will be interesting to see if these young quarterbacks can conquer the eight-man fronts.
John Clayton, a member of the Pro Football Hall of Fame writers' wing, is a senior writer for ESPN.com.