Just trade him! It’s not that simple.

There’s good reason star-for-star trades are a rarity in the NFL

The Vikings have a star-studded dilemma in Minnesota: Sign Percy Harvin to a multiyear deal, let the much-maligned wide receiver play out the final year of his contract or trade him. “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,” former NFL general manager and current NFL analyst Bill Polian said. Enlarge photo

Andy King/Associated Press file photo

The Vikings have a star-studded dilemma in Minnesota: Sign Percy Harvin to a multiyear deal, let the much-maligned wide receiver play out the final year of his contract or trade him. “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,” former NFL general manager and current NFL analyst Bill Polian said.

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 ballcarrier, 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 likely again will 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 probably is 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 in a phone interview. “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 talent pool in baseball, that sport 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 was 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, such as Anquan Boldin and Marshawn Lynch.

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 typically are worth a lot more in the NFL blue book than players five years in.

“The new team that would be getting Percy Harvin is going to get him for retail, as opposed to discount,” Brandt said in a phone interview. “And that’s a factor. I’m not the best person to judge if he’s one of the top receivers, but I know enough that he’s a talent, and he’s a special player. So he’s going to want to be paid like a special player.”

Ah, yes. The money factor. No team would acquire him without agreeing to an extension first, another potential trade inhibitor, given the risk he’d leave through free agency a year later.

Plus, if the Vikings actually were able to find an available star such as Fitzgerald, there’s another roadblock to a deal.

If a player is cut or traded before the end of his contract, the team that gets rid of him must count all the unaccounted-for bonuses against the salary cap. If a player got a $10-million bonus over a five-year deal and was traded after three seasons, that’s a $4-million cap hit to the jettisoning team. Dead money is a major hindrance to building a quality roster.

“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.”

Very few deals are star for star, unless the star developed from a draft pick; Clinton Portis (Denver to Washington) for Champ Bailey (Washington to Denver) is one of the few modern examples of that. Enlarge photo

Stephan Savoia/Associated Press file photo

Very few deals are star for star, unless the star developed from a draft pick; Clinton Portis (Denver to Washington) for Champ Bailey (Washington to Denver) is one of the few modern examples of that.

When the Denver Broncos traded star quarterback Jay Cutler to the Chicago Bears, they got a significant return – but no star players. And there’s good reason star-for-star deals are rare in the NFL. Enlarge photo

Nam Y. Huh/Associated Press file photo

When the Denver Broncos traded star quarterback Jay Cutler to the Chicago Bears, they got a significant return – but no star players. And there’s good reason star-for-star deals are rare in the NFL.

Former Denver Broncos and Miami Dolphins wide receiver Brandon Marshall is a rarity in the NFL; he’s been traded twice, as many times as Randy Moss, in a league that very rarely moves its star players. Enlarge photo

Charles Rex Arbogast/Associated Press file photo

Former Denver Broncos and Miami Dolphins wide receiver Brandon Marshall is a rarity in the NFL; he’s been traded twice, as many times as Randy Moss, in a league that very rarely moves its star players.