Souhan: Vikings' Peterson has been looking merely mortal this season

Two unrealistic and entirely theoretical football-based conversations have hovered around Adrian Peterson this season, flitting from Twitter timeline to talk show.

The first, which became popular with Vikings fans this summer, asked whether Peterson could rush for 2,500 yards this season.

The second, prompted by the nature of the NFL and renewed by the Vikings' offensive failures, asks whether the Vikings should trade Peterson for a quarterback.

Like alien spaceship sightings and sasquatch rumors, there is enough raw logic and circumstantial evidence surrounding the questions to make them sound legitimate, even if both are as improbable as an alien sasquatch cooking you dinner tonight.

The first question has been rendered rhetorical by the stunning failure of the Vikings' offensive line to open holes against stacked defensive fronts, one season after the line did exactly that while enabling Peterson's 2,097 rushing yards in 2012.

The second question becomes more logical every week.

Should the Vikings trade Peterson for a quarterback?

In the purely theoretical world in which the Yankees and Red Sox should have swapped Joe DiMaggio and Ted Williams, to allow each to hit in a ballpark more suited to their swings, the Vikings should trade Peterson for an elite quarterback.

Here's the problem: It's a good idea for the Vikings because it would be a bad idea for any trade partner. As great as Peterson is, no intelligent NFL general manager would trade an elite quarterback for a running back, even the greatest running back of a generation.

And even if the Vikings could get someone to stay on the phone for five seconds to listen to their pitch, Peterson has less trade value than he's ever had.

What made Peterson's MVP season so surprising was his ability to beat defenses dedicated to stopping him, ones that saw no number other than 28 when they practiced all week.

Monday night, Peterson's season of frustration reached its lowest valley. Facing a poor defense on a national stage, he managed 9 rushing yards on eight carries in the first half and 28 for the game.

Instead, Peterson's season has reversed his saying. It's been "Feast, famine, famine.'' He took the first handoff of the season 78 yards for a touchdown. Since then, he has averaged 3.8 yards per carry, a shocking number for a back who often creates his own space by breaking tackles and bouncing runs away from designed paths.

The Vikings' unsightly passing offense could be blamed, if Peterson hadn't thrived regardless of the state of the passing game last year.

The Vikings' coaching staff could be blamed, but these coaches were all in place last year.

So what's changed?

The same offensive linemen who seemed to surge off the line of scrimmage last year too often are losing the primal competition between the tackles this year. Too often, Peterson takes hits before he reaches the line of scrimmage, or reaches the line to find only opponents' jerseys. Monday night, Peterson said he would discuss the lack of physical play with the linemen.

He doesn't look like Adrian Peterson.

His 2012 season made Peterson seem superhuman, the way he recovered from major knee surgery ahead of schedule to challenge the all-time rushing record, the way he propelled a team that won three games in 2011 and has won one game this season to the playoffs.

This season, since that first run, Peterson has looked decidedly mortal.

He's been limited by a sore hamstring. He has absorbed the loss of a son, which left him open to tabloid questions about his personal life.

Peterson has been a star for so long it's easy to forget that he's only 28. He should have plenty of good years ahead of him, even at a position that chews up body parts like a "Walking Dead" extra.

Peterson's running as if he's wearing a lead vest and ankle weights. That is the most surprising of the Vikings' many problems.