In an age of designer steroids engineered to beat stringent testing, the anabolic steroid Stanozolol existed for years as a chemical relic. Testers had been catching it in athletes since the 1988 Seoul Olympics, when sprinter Ben Johnson lost his gold medal. Mentions of Stanozolol peppered the Mitchell Report, but it rarely surfaced in baseball once the sport instituted drug testing. Stanozolol worked, but it would also get you suspended, so it largely disappeared.

All of which made this spring so puzzling and, for baseball, so potentially troubling. In the span of 17 days between March 27 and April 11, Major League Baseball suspended four players 80 games for failing a performance-enhancing drug test. The players – Mets closer Jennry Mejia, Twins starter Ervin Santana, Braves reliever Arodys Vizcaino and Mariners reliever David Rollins – all tested positive for Stanozolol.

The spate of failed tests both vexed the sport and moved the league to action. MLB launched an investigation based on the model the league used to thwart Biogenesis, the purported aging clinic that peddled testosterone and human-growth hormone to several players, Alex Rodriguez most infamous among them.

“Other than the similarity of substance, I have no reason to believe right now that [the positive tests] are connected,” Manfred said Monday in Toronto, according to the Associated Press. “Having said this, whenever we have a series of tests for a single substance, we undertake an investigative effort to determine whether there’s a connection and what that connection might be. If you look back, the very beginning of Biogenesis was the fact that we had a series of testosterone positives that began our investigative process, so we’ll follow that same model.”

Major League Baseball has not “established anything yet” in its investigation, said a person familiar with the situation, who declined to speak publicly because the situation is ongoing. The league has yet to speak with the four players who tested positive, but hopes to in the near future.

The resurgence of Stanozolol baffled experts and prompted speculation. Charles Yesalis, a longtime Penn State professor and consultant to sports leagues and government agents on issues pertaining to steroids, refuses to believe the positive tests couldn’t be somewhat related. How they might be related, though, is another question.

“I have no clue, because this is weird,” Yesalis said. “I don’t know this commissioner, and I don’t care what the hell he says. There is no way, in my mind, this is one big coincidence.”

Sold as Winstrol, Stanozolol is commonly ingested in tablet form and can also be injected. It is known as a “cutting steroid” because of how it promotes fat loss and building lean, hard muscle. It’s most damaging negative side effect is liver failure. Tests catch it easily because it remains in a user’s system for a long time.

“It’s an old-school steroid that would have given them a big advantage,” Untied States Anti-Doping Agency CEO Travis Tygart said in a phone conversation.

The Mitchell Report cited five major leaguers, including Jose Canseco, who had used or purchased Stanozolol. But MLB had not suspended any major league player for the substance since Rafael Palmeiro received a 10-game ban in 2005.

“It really is hard to explain,” Manfred said on opening day at Nationals Park, before Mejia’s failed test. “Because the particular drug involved is one that’s not particularly hard to catch in a drug test.”

Tygart, who is often tough on leagues’ testing policies, praised MLB’s drug program and believed the suspensions reflected a tough policy, particularly its offseason testing. He expressed optimism MLB would get to the bottom of why the positive tests had occurred.

“It’s bittersweet,” Tygart said. “You’re disappointed on the one hand. On the other hand, when they make that decision and they’re caught, that’s a good outcome for clean athletes. Every issue brings to mind more issues you want to know more about and investigate.

“In this business, we’ve seen enough to know you don’t rule anything out and rule anything in. The fact that it’s the same substance in and of itself doesn’t suggest anything more than you need to follow up on the investigation.”

The tests begged many questions and raised several theories. A handful of minor league players have been caught using Stanozolol over the years, including Yankees pitcher Bryan Alcantara in March. A handful of minor leaguers have been caught with the substance over the years  — most of them from the Dominican Summer League, which is not a coincidence given how prevalent the drug is on the island.

But minor leaguers are younger, have less access to expensive, underground chemists and are more desperate to take a risk. Major leaguers, who tend to be, but are not always, more sophisticated, would not rationally use Stanozolol.

“Guys like that do not do what I refer to as ‘cowboy chemistry,’ ” Yesalis said. “They don’t go down an alley and a guy named Lenny goes, ‘Look what I got for you.’ That’s what befuddles me about this. They can afford not to do dumb things.”

The four major leaguers share no common connection, although three of the four hail from the Dominican Republic. Stanozolol is readily available in the Dominican, and the country has standards for both labeling and selling supplements.

Both Mejia and Santana accepted their punishment but insisted they had not knowingly taken a banned substance. But experts — and the league — doubt they  purchased an otherwise legal supplement that had been tainted with Stanozolol, or a supplement they believed wouldn’t contain banned substances that didn’t list all its ingredients.

“That’s hard to believe, in a way,” Yesalis said. “I can’t see elite athletes using anything but supplements from the most bona fide, reputable supplement companies. Why would those kind of companies have Stanozolol on hand?”

For that reason, Tygart said, it is exceedingly rare for an over-the-counter supplement to be contaminated with Stanozolol.

An illicit supplement producer, though, would have Stanozolol on hand, which raises the most distressing possibility for baseball: the players used what they believed to be designer steroids, but were caught only because the drugs had been mistakenly tainted with Stanozolol by a sloppy chemist.

“It could be contamination by an underground steroid lab not cleaning their glassware thoroughly and getting Stanozolol contamination,” Victor Conte, the former owner of the infamous BALCO clinic, wrote in an email.

For now, theory trumps hard evidence. The rash of Stanozolol suspensions has not mushroomed into a fully formed dark cloud the way the Biogenesis scandal did. Baseball is trying to find out what exactly is going on before it can.

“Performance-enhancing drugs is one of those areas where you have to stay vigilant,” Manfred said. “Things happen that you don’t expect. But we have a great testing program with great investigative capacity, and if the players take the risk, we feel we’re going to catch them.”

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