When quarterbacks turn 38 years old, it's like their throwing arm has fallen off. Like they've taken a long walk off a short pier. Like their supercharged sports car just ran out of gas.
This phenomenon was detailed by the Chicago Tribune's Don Pierson in the days before the Packers visited Chicago in the regular-season finale.
The question is this: When Favre turns 38 on Oct. 10, will his career tumble like a stone hurled off a mountaintop? Or will he ignore this barrier like he has the notion that a quarterback can't possibly start 16 games per season, for season after season?
The latest example is Minnesota's Brad Johnson.
When Daunte Culpepper went down with the most serious of knee injuries, Johnson started the final nine games of the 2005 season for the Vikings at the age of 37. By completing 62.6 percent of his passes, with 12 touchdowns, four interceptions, an 88.9 rating and a 7-2 record, Johnson was given the job for 2006, and the Vikings sent Culpepper to Miami.
Johnson played one more game as a 37-year-old. He compiled an 88.6 rating with one touchdown and no interceptions in a victory over Washington. Johnson turned 38 on Sept. 17, and he started 13 more games before losing his job. Only twice did he surpass his season-opening passer rating, and he finished the season with nine touchdowns and 15 interceptions.
Most quarterbacks — most players, for that matter — retire before they hit the 38-year-old barrier.
The ones that do — with only a few exceptions, such as John Elway winning Super Bowl XXXIII as a 38-year-old — fail. Most of them, even the following Hall of Famers, fail miserably.
Joe Montana, perhaps the greatest quarterback ever, was 38 during his final season. His 83.6 passer rating with the Chiefs wasn't bad, but he had only one season that was worse.
Dan Marino turned 38 two weeks into his final season. He finished his career with a more than 2-to-1 touchdown-to-interception ratio, but in 1999, he tossed 12 touchdowns and 17 interceptions. His passer rating of 67.4 was more than 12 points worse than his previous career low.
Fran Tarkenton turned 38 during his final season. In three seasons from ages 35 to 37, he threw a combined 35 interceptions. At age 38, in his final season, he threw 32 interceptions.
When he was 37, Johnny Unitas led the Baltimore Colts to the championship. In his final three seasons, from ages 38 to 40, Unitas threw a combined 11 touchdowns and 22 interceptions.
When he was 37, Y.A. Tittle led the Giants to the championship. When he was 38 and in his final season, his Giants finished 2-10-2.
In his final three seasons, from ages 38 to 40, Len Dawson threw 14 touchdowns and 22 interceptions for the Kansas City Chiefs.
If the Packers are to threaten for a playoff spot in 2007, the Packers need Favre to ignore the 38-year-old barrier. Warren Moon is the only modern-era Hall of Fame quarterback to truly blow through that barrier. In his first full season as a 38-year-old, Moon threw for 4,228 yards, 33 touchdown passes and 14 interceptions for the Vikings in 1995.
Packers general manager Ted Thompson thinks Favre can succeed where so many others have failed.
"I haven't seen any evidence of any declining physical ability for him to play the game," he said. "I think he's one of those rare birds that you see once in a generation that can play at a very very high level for an extended amount of time. Now, when that time comes for him, not to be able to produce that way, I don't know when it's going to be, but I don't see any evidence of it."
Steve Lawrence is a regular contributor to PackerReport.com and Packer Report magazine. Send comments to firstname.lastname@example.org.