John Clayton's 'Theory of 150' for O-lines

ESPN.com senior writer John Clayton has theories on questions you've never thought of asking, and here is one of particular note to NFC North teams. When evaluating the future of an offensive line, Clayton writes, teams would be wise to follow the "Theory of 150."

Here's how Clayton explained it: "If a team lets its starting offensive line exceed the total age of 150 years for five starters, the clock is ticking on its remaining success."

A cumulative age of 150 means an average age of 30 for five starters, an intuitive if arbitrary benchmark for signaling transition. As Clayton notes, there is one NFC North team that exceeds the limit: the Detroit Lions, whose five starters total 152 years old.

The Lions have already started the process of getting younger, having drafted Riley Reiff as a possible replacement for 34-year-old left tackle Jeff Backus. Even so, they still have a 33-year-old center Dominic Raiola and a 30-year-old right guard in Stephen Peterman.

The Theory of 150 also helps explain why 2012 was the right time for the Minnesota Vikings to overhaul their line. Last year's starters, which included left guard Steve Hutchinson (34) and right guard Anthony Herrera (32) would have combined for an age of 147 when the 2012 season began. By drafting left tackle Matt Kalil and moving Charlie Johnson (28) to left guard, the Vikings ensured themselves of the youngest offensive line in the NFC North this season. (Geoff Schwartz, who will be 26 in Week 1, or Brandon Fusco, 23, will start at right guard.)

The Green Bay Packers, meanwhile, brought their cumulative age down from 140 by replacing left tackle Chad Clifton (36) with Marshall Newhouse (23). The Packers stand at 133 because new center Jeff Saturday will be 37 in Week 1, but it's worth-noting the second-oldest Packers offensive lineman is right guard Josh Sitton at 26.

Finally, the Chicago Bears are expected to have two starters of at least 30 years old -- left guard Chris Spencer and center Roberto Garza. Their cumulative age will be 138 with J'Marcus Webb at left tackle and 141 if Chris Williams wins the job.

As with anything, the "Theory of 150" is more relevant for some teams than others. The line is a position group where younger isn't always better; the fading of speed and athletic ability don't affect linemen as much as running backs, receivers and other skill positions.

But if you are a team that wants to plan orderly transitions, the "Theory of 150" is a decent benchmark for timing. Whether or not we added the cumulative ages of the Lions' linemen, we could eyeball the roster and know it's time to begin the process. In that regard, Reiff was drafted at an ideal time. So was Kalil in Minnesota, and it's not surprising to see the Packers move on at left tackle as well.

Soon, we'll move on to the "Theory of 10:" How watching 10 hours of television a day is a sign it's time to find a hobby.