Why is MLB’s pursuit so intense?

The information was impossible to ignore.

Baseball could not simply dismiss the original Miami New Times report alleging that players had purchased performance-enhancing drugs from Biogenesis, an anti-aging clinic in the Miami area.

Not if the sport was serious about cracking down on PED use. Not when the founder of the clinic, Anthony Bosch, was the son of a doctor who allegedly wrote a prescription to Manny Ramirez for female fertility drugs in 2009 — and served as a middle man between the two.

No, baseball had to proceed.

But why are the sport’s top officials pursuing the case with such intensity? Why are they cutting a deal with Anthony Bosch, whose credibility, if it were a batting average, might be below .200?

Those are the biggest questions in the aftermath of baseball reaching agreement with Bosch to testify about his dealings with players, as first reported by ESPN.

And the answers rest with commissioner Bud Selig.

It is Selig — and Selig alone — who has the power to suspend players under the joint drug agreement even if they do not test positive; a player is subject to disciplinary action for “just cause” by the commissioner if sufficient evidence exists that the player used, purchased or distributed banned drugs.

And it is Selig who might be trying to cement his legacy as the commissioner who attacked PEDs; he drew heavy criticism when the use of such drugs erupted under his watch in the late 1990s and early 2000s.

Selig plans to retire in January 2015. He already has served as a driving force in baseball adopting a drug-testing program that is widely viewed as the toughest in North American professional sports.

The suspensions of the Brewers’ Ryan Braun and the Yankees’ Alex Rodriguez — two superstars who, in baseball’s view, might have lied about their alleged use of PEDs — would leave a lasting memory of a commissioner who did everything he could to fix the problem.

Braun became the first player known to win an appeal of a positive drug test in February 2012, prompting baseball to issue a statement saying it “vehemently disagreed” with the decision of the arbitrator, Shyam Das. Baseball fired Das three months later, and Braun further angered baseball by saying his test was “fatally flawed.”

Rodriguez spoke to investigators from baseball after admitting to using PEDs during a three-year period beginning in 2001. His answers apparently satisfied Selig; he was not suspended. But his alleged link to Biogenesis raises new questions about whether he was being truthful.

Some on the players’ side use the term “witch hunt” to describe the fervor of baseball’s pursuit of Braun and Rodriguez. Certainly, the sport is taking unusual measures in its attempt to tie those two — and other players — to Biogenesis.

Baseball cut an extensive deal with Bosch in exchange for the information that he will provide, according to ESPN. The agreement includes promises that baseball will drop its lawsuit against Bosch, reimburse him for any liability arising from his cooperation, provide him with personal security and even assist him with law-enforcement officials who might want to speak with him.

The New York Daily News reported Thursday that Bosch made his deal with baseball only after Rodriguez rejected his plea for financial help — help that Bosch needed to fight baseball’s lawsuit against him.

“They were afraid someone else would pay him,” a source told the Daily News. “Bosch is the only guy that can provide them with what they need.”

Baseball, however, sued Bosch in March for “intentional and unjustified tortious interference” with contracts between teams and players by providing players with illegal substances.

And now he will be a trusted witness for baseball against the players who allegedly who were his customers?

If baseball indeed pays Bosch for testimony, it will raise further questions about Bosch’s credibility and might even be considered improper, according to some on the players’ side. The union would learn of such payments through cross-examination of Bosch, or perhaps by seeking a deposition from him before he testifies, a source said.

Yet, the union is not simply preparing to pounce; it is adopting a “wait and see” approach while bracing for the evidence that baseball will present against the alleged users. As union chief Michael Weiner said in a statement Wednesday, “The Players Association has every interest in both defending the rights of players and in defending the integrity of our joint (drug) program. We trust that the Commissioner’s Office shares these interests.”

While baseball’s frustration with Braun and Rodriguez seems evident, it is doubtful that the commissioner’s office entered into its agreement with Bosch recklessly; rarely in the union’s estimation does the sport seek “cowboy” justice.

Indeed, the relationship between the union and commissioner’s office is much stronger than it was when Donald Fehr headed the union and fought drug testing at every turn. The culture of the sport also is different.

Union officials say the vast majority of players want a clean sport — and that if baseball presents sufficient evidence and follows due process, the union will have no problem with suspensions stemming from the joint drug program.

Right now, all of that is a big “if.”

Baseball has yet to meet with Bosch. The union has yet to see baseball’s evidence. Only one thing is clear — none of this would be happening if Selig did not want it to happen.

His legacy is at stake.