Childress Index favors Favre

During my trip to Vikings training camp this summer, I met with Minnesota coach Brad Childress. Not knowing then that Brett Favre would end his retirement and sign with the Vikings, we discussed expectations about quarterbacks.

He mentioned a simple theory that seems to work that I had never heard before. The formula seems almost too basic, but upon further review, it's telling. If a team's combined number of rushes and pass completions is around 50, it will win most games.

Having spent the morning gazing at a practice field loaded with offensive talent, my mind wandered. The Vikings are deep at wide receiver and tight end and have the best running back in football in Adrian Peterson. Put Favre in charge of that offense, and the Vikings should be a 12-win team, right? Starting Tarvaris Jackson or Sage Rosenfels would probably mean a nine- or 10-win season and a first-round playoff loss -- if the Vikings made the postseason in the now-tougher NFC North.

Suddenly, it hit me why it's obvious Favre is the answer for Minnesota, and not Jackson or Rosenfels. The Vikings, thanks to Peterson and Chester Taylor, averaged 32.438 runs a game last season. Gus Frerotte and Jackson averaged 16.69 completions, giving the Vikings the 49.13 combination that made them a winning team. Though the Eagles team that beat them in the first round of the playoffs had a 49.31 combination, Donovan McNabb averaged 22.63 completions a game. That's six completions a game better than the Vikings and a key reason why McNabb beat Minnesota in the playoffs last season, according to Childress.

"I think to start things, it's great to play great run defense and run the ball," Childress explained. "You can do it in the dome and in games outside. But to be able to score a high number of points somewhere, you've got to pass the ball. And I'm not saying with the play-action pass."

That got me to thinking about the Vikings' addition of Favre, who averaged 21.4 completions a game last season for the Jets. Add Favre to the Vikings, and the Childress Index should soar into the 50s.

Going through numbers over the past five seasons, the 26 playoff teams that topped 50 averaged a 12-4 record. The 2005 Redskins were the only playoff team that topped 50, but didn't win at least 10 games.

I left Mankato, Minn., thinking the Vikings had to get Favre to compete in a division with Jay Cutler in Chicago and Aaron Rodgers in Green Bay. Jackson has had only three 20-completion games during his NFL career, which is pretty much the norm for quarterbacks with four years of experience or less. Heck, over the past two years, he's only had nine games in which he's completed 16 or more passes.

Given Childress' index of completions and running attempts, I wanted to study a few different scenarios around the league -- past and present. Several things ended up making sense.

It's easy to see why Ben Roethlisberger, Matt Ryan and Joe Flacco have had early success. They played for running teams that took pressure off them.

Ryan's Falcons ran the ball 35 times a game last season. He completed 16.56 passes a game, good enough to put the Falcons (11-5) among the elite teams in the NFC. Flacco had it even easier. The Ravens averaged 37 rushes a game in 2008. Flacco completed only 16.06 passes a game as the Ravens went 11-5 and advanced to the AFC Championship Game.

Go back to Roethlisberger's rookie season in 2004. The Steelers averaged 38.6 rushes a game. All they needed were 10 completions a game for the Steelers' offense to be good. The Steelers had 14.25 completions a game and went 15-1.

During Roethlisberger's five years, the Steelers have averaged 32.59 rushes a game, giving Roethlisberger a chance to grow as a quarterback. His completions have grown from 14 a game to anywhere between 17 and 19 over the past three years.

"I don't have a grand number of rushes you need to be a successful offense," Childress said. "Usually, you'd like to run it 25 to 30 times a game. If you are doing that, you either have the lead or you are able to exert your will on somebody."

It's also easy to see why the Jets can justify starting rookie Mark Sanchez, while the Lions must cringe at the thought of serving up Matthew Stafford as the starter.

The Jets have averaged 28.375 rushes a game over the past five years and have three good running options: Thomas Jones, Leon Washington and Shonn Greene. They would need about 19 completions a game to be a winning team, but you figure most rookies get about 16. However, at least the Jets have a chance to be successful on offense with Sanchez because of the running game.

It's hard to make that argument in Detroit, even though the Lions have a talented running back in Kevin Smith. Over the past three seasons, the Lions have averaged 22, 20.25 and 19 rushes a game. Their Childress Index numbers are 39.56, 43.25 and 42.25.

For the Lions to be a successful offense, Stafford would have to average around 26 completions a game. Only three teams have done that over the past five seasons; two of those teams had losing years.

One scary thought for Childress and the Vikings is the impact of Cutler on the Bears' offense. Cutler averaged 20.38 completions a game in 2007 and 24.13 last season. Over the past five years, the Bears have averaged 28.475 rushes a game. If he can average 22 completions a game, the Bears will be right with the Vikings. Rodgers averaged 21.44 completions a game in his first season as Packers starter and looks even better this summer.

Just another reason why Favre makes perfect sense for Minnesota.

John Clayton, a recipient of the Pro Football Hall of Fame's McCann Award for distinguished reporting, is a senior writer for ESPN.com.