NEW YORK (CNN/Money) - Red Sox fans, including my wife and in-laws, won't want to hear this, but the Major League Baseball Players Association had no choice but to block the deal to send Alex Rodriguez to the long-suffering team.

Rodriguez, baseball's best paid player, had agreed to changes in his 10-year, $252 million contract demanded by the Red Sox owners to do the deal and get him away from the Texas Rangers.

Alex Rodriguez

But the union stepped in Wednesday, saying the way the deal was restructured would cut the value of the contract, which is not allowed under the collective bargaining agreement. Commissioner Bud Selig announced Thursday evening that he had withdrawn permission for the Sox and A-Rod to pursue the trade, with Major League Baseball President Bob DuPuy criticizing the union for its actions.

This has turned the good liberals of New England into union-haters worthy of Sam Walton or, well, Bud Selig. The Boston Globe compared the union's lawyer who announced the decision to Scrooge.

"It is a sad day when the Players Association thwarts the will of its members," said Red Sox CEO Larry Lucchino. "The Players Association asserts that it supports individual negotiations, freedom of choice, and player mobility. However, in this high-profile instance, their action contradicts this and is contrary to the desires of the player."

Meanwhile, the decision could lead the rival Yankees to switch theme songs. Instead of playing "New York, New York" at the end of every game, the Bombers might now consider that traditional labor ballad, "Look for the Union Label."

It's easy to understand the anger in Boston. It seems ridiculous that a union should be able to stop a multi-millionaire from accepting fewer millions to play a game most fans would gladly play for free.

But the MLBPA is a union, and the purpose of any union is to act in the best financial interests of its members. Even if A-Rod doesn't need its help, it has hundreds of other members who do.

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The fact is, allowing players to agree to cuts in their own salary is the first step down the road to making their contracts -- both big and relatively small -- as worthless as Red Sox 2003 World Series tickets.

If you have any doubt that players less wealthy than Rodriguez could be forced to take less than their contract called for, ask players in the National Football League. They are regularly being forced to take substantial pay cuts to hang onto their jobs.

Yes, it's true that the NFL players have non-guaranteed contracts and a salary cap working against them. But the MLBPA didn't win a stronger labor deal for its members by giving unilateral concessions to make specific teams or star players happy -- which is what Red Sox fans would like to see the union do here.

If A-Rod is allowed to agree to pay cuts, other players could soon be forced to take pay cuts as well. Few of them would negotiate from as strong a position as Rodriguez, who is arguably the league's best player.

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"The union can't allow this to set a precedent," said Doug Pappas, a New York attorney and an expert in baseball salary structure and economics.

If players could negotiate a reduction in their contracts, he said, "instead of teams eating salaries the way they do currently when they dump salaries in these trades, they'll demand the savings come from the players."

Now, I'll freely admit to cheering for the team that stands to benefit most from this decision -- the Yankees. But Pappas is among the biggest Yankee haters I know. He agrees this decision is about far more than which team will get to overspend the most in the sports' most heated rivalry.

"The union wants the sanctity of the contract as drafted," Pappas said. "Strictly speaking, the players aren't empowered to negotiate such things (i.e., reduced benefits)."

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Players agree to take less than top dollar all the time, and the union can't and doesn't say anything about it. Former Yankee pitcher Andy Pettitte, for example, signed with his hometown Houston Astros this winter for far less than the Yankees were willing to pay.

If A-Rod wanted to take less that the top possible dollar in order to play for a better team, the time for him to decide that was before he signed the deal, not three years later. He seemed ready to acknowledge as much on Thursday.

"In the spirit of cooperation, I advised the Red Sox I am willing to restructure my contract, but only within the guidelines prescribed by union officials," Rodriguez said in a statement to the media. "I recognize the principle involved, and fully support the need to protect the interests of my fellow players."

If the Red Sox really wanted to have him next year, they knew the cost before they started these trade talks. For the club to blame the union now is like blaming Babe Ruth for the team's troubles the last eight decades.

In other words, union-bashing makes the fans feel better without having much to do with the truth.