MINNEAPOLIS – On many Sundays, the Minnesota Vikings have been happy to have Percy Harvin wearing a purple jersey.

These days he represents a dilemma.

The Vikings can try to sign the multi-talented but moody wide receiver to a contract extension before the season begins for the big money he’s sure to command. That means making a long-term investment in a player whose punishing running style increases his chance of injury and who has clashed at times with coaches.

They could let the last year of his current contract play out and brace for that potential distraction that comes with that move, risking the possibility he’d hold out of training camp without a new deal.

Or they can try to trade him, even though a top Minnesota executive has made it clear that’s not what the team wants to do.

Harvin is a sure-handed, pass catcher who can run effective routes all over the field. He’s a speedy yet hard-nosed ball-carrier, capable of lining up as a running back. He’s a touchdown-threat kickoff returner. He played so well during the first half of the 2012 season that he was part of the NFL Most Valuable Player award conversation before he badly sprained his ankle.

He will turn only 25 on May 28. Most teams in the league would love to have his diverse skills.

This doesn’t mean Minnesota would find it easy to trade Harvin for equal value if he’s not included in the future core.

Vikings fans remembering the seventh overall draft choice that Randy Moss fetched from Oakland in 2005 might hope for the same return from Harvin or dream of a deal with Arizona for Larry Fitzgerald, a native of Minneapolis. But the reality of the NFL is headliner trades will likely again be rare once the market opens March 12. Because of the team-to-team differences in schemes, the complications of the salary cap and the precious resource that draft picks have become, this league is not much for wheeling and dealing.

While Harvin might have played his last game with Minnesota, the chance of him continuing his career with the club that made him the 22nd overall pick in the 2009 draft is probably just as good.

“Again, there is no intent to trade Percy Harvin,” Vikings General Manager Rick Spielman said Friday. “He is a very good football player.”

Former Indianapolis executive Bill Polian, now an analyst for ESPN, cited a mantra often uttered by former coaches George Allen and Marv Levy.

“Nobody trades you anyone they think can help them,” Polian said. “So that’s sort of been the ethos of the NFL for a long time. People, unlike basketball and baseball, are inherently wary of making trades. System fit is really, really important, far more than the average fan knows.”

Teams that use a 3-4 alignment on defense have less use for a defensive end in a 4-3 scheme. Teams that prefer a traditional pocket passing game won’t want an option-style quarterback.

“It’s the same reason, in my opinion, why free agency doesn’t work well in the NFL,” said Andrew Brandt, a former contract negotiator and salary-cap manager in Green Bay who’s now an NFL business analyst for the National Football Post website and ESPN. “Players have to fit in with 10 other independent parts, and it’s just not seamless like it is in basketball or baseball. If you’re a baseball pitcher, you go from one team to another and you do the exact same thing. If you’re a linebacker, you go from one team to another and you’re not doing the same thing, even though you may think you are.”

With rosters twice as big in pro football, there are more than two times as many active players in the NFL than in Major League Baseball. But according to STATS research, there were only 448 players traded in the NFL over the last 10 years. In MLB? A whopping 2,362 players were dealt, according to STATS. While minor leaguers broaden the baseball talent pool, it still has a much higher rate of trades.

And in baseball, teams can’t trade draft picks, so every deal is a player-for-player swap. In the NFL over the last 10 years, according to STATS, there were only 44 player-for-player deals that didn’t involve draft picks.

Sure, Moss has been traded twice now. So has Brandon Marshall. Jay Cutler brought Denver a significant return, as did Jared Allen for Kansas City. But none of those deals were star for star, unless the star developed from a draft pick. Clinton Portis for Champ Bailey is one of the few modern examples of that. Several standouts have switched teams in recent years but for mere mid-round selections: like Marshawn Lynch and Anquan Boldin.

If speed is the most coveted asset in this league, youth is right behind. Plus, under the new collective bargaining agreement that limits the size of signing bonuses, first-round talent is cheaper than before. Players are a little like cars. Shiny new first-round draft picks driven right off the dealer’s lot are typically worth a lot more in the NFL blue book than players five years in.

“You presume a draft choice is going to net you four to five years,” Polian said. “So you’re saying, ‘Is this particular player going to net us four to five years at this stage of his career, and are we reaching ourselves going forward by making this transaction now?’ It isn’t the kind of stuff that you discuss over the dinner table or a drink after work: ‘Should we trade ‘Player A’ for ‘Player B?’ It’s far more complicated than that.”

PACKERS: Before surfing into the locker room at Lambeau Field, Charles Woodson paused for a moment of reflection. He stretched his arms out, yelled and basked in the glow of a home playoff victory over the Minnesota Vikings.

Maybe he knew it. Maybe not. But this was Woodson’s final farewell. On Friday, it became official. After a seven-year run packed with highlights, Woodson was released by the Green Bay Packers.

Since 2006, he has crafted a Canton-worthy resume. A Super Bowl title in 2010. Defensive player of the year honors in 2009. More than 100 games full of momentum-changing turnovers. Initially lukewarm about playing in Green Bay, Woodson enjoyed a career renaissance. But he also turns 37 in October. For Green Bay, it was time to move on.

Woodson has no plans to retire. Agent Carl Poston said his client will forge ahead for a 16th NFL season. Woodson hopes to sign with a contender and pursue a second Super Bowl.