Whenever baseball players make the poor decision to use a banned substance — wittingly or not — they immediately sign themselves up to grapple with a series of trickier decisions. First up: How do you explain the positive test, and what exactly do you admit to?

After a positive test for the anabolic steroid clostebol ended his 2022 season before it started — and rocked a sport awaiting his return to the star-studded San Diego Padres — Fernando Tatis Jr. went with “carelessness.” He said in a statement released by the union Friday night that he “inadvertently took a medication to treat ringworm.” His father, the former major leaguer Fernando Tatis Sr., expounded on that explanation Monday, telling media in the Dominican Republic that Tatis Jr. got the fungal infection on his neck from a haircut and used a spray called Trofobol to treat it.

The recklessness won’t be a comfort to the Padres, who signed Tatis Jr. to a 14-year, $340 million contract about 19 months ago. Especially since it’s becoming a pattern for the 23-year-old, who had been out with a wrist injury likely sustained in a motorcycle accident (or accidents), and San Diego president of baseball operations A.J. Preller spoke candidly about a lack of trust between team and player. But as excuses for steroid use go, copping to a negligent use of medicine is a fairly straightforward one. It avoids one of the major pitfalls former major leaguers like Alex Rodriguez, Ryan Braun and Melky Cabrera fell into — lying about it, directing blame toward someone else, or even creating entire fake websites to cover their tracks.

There’s no easy path back into the good graces of his teammates or fans, but accepting responsibility, as Tatis Jr. did, is usually the most direct route toward forgiveness.

As long as you trust the story.

That can be hard to parse when unfamiliar drugs, fungal infections and the nuances of anti-doping testing are involved. We asked anti-doping expert Oliver Catlin, president of Banned Substances Control Group (BSCG), to help us understand the stated sequence of events that led to Tatis Jr.’s 80-game suspension.

What is clostebol, the steroid Tatis Jr. tested positive for?

Tatis Jr.’s statement owned up to a mistake, even as it raised some more questions about how he wound up in position to make it. His father’s explanation … took on more of an aggrieved tone, castigating MLB for suspending his son over a substance he called insignificant.

“This is a catastrophe what has taken place, not just for Jr., but for all of baseball. There are millions of fans who are gonna stop watching baseball now,” Tatis Sr. said, as relayed by ESPN. He went on to claim that “what came out positive in Jr.'s body is something that doesn't give you strength.”

That claim about millions of fans turning away from the sport is hyperbolic and wildly unlikely, but his larger point focuses on whether clostebol, the steroid that showed up in Tatis Jr.’s sample, is actually potent enough to warrant the suspension and black mark on his son’s name. First, clostebol is directly listed as a banned anabolic steroid in MLB’s Joint Drug Agreement, so having it in your system is going to get you suspended. There’s no room for confusion.

Now, Tatis Sr. is not wrong about its effects being minor compared to other performance-enhancing drugs. Catlin said clostebol is “generally considered a weak anabolic steroid.”

“Frankly, it wouldn’t make much sense to use it if you were really trying to build muscle as there are much more powerful and effective anabolic steroids that are easily available,” Catlin told Yahoo Sports. “Oral turinabol, for example, also found frequently in MLB, is a much stronger drug and would be a more likely anabolic steroid to be used.”

A guide to the drug directed at bodybuilders said, “if you are looking to pack heaps of muscle mass onto your body, clostebol is not the steroid for you,” but called it ideal for building “moderate amounts of lean muscle, while burning fat and improving athletic performance.”

The other notable baseball players to test positive for clostebol are the relatively light-hitting middle infielders Dee Strange-Gordon and Freddy Galvis.

Was Tatis Jr. actually enhancing his performance?

A positive PED test calls to mind the tainted sluggers of the 1990s, and could lead fans to question the historic start of Tatis Jr.’s career. He paced the National League with 42 homers on his way to a third-place NL MVP finish in 2021, and no MLB player has ever matched his 81 homers and 52 stolen bases in their first 300 career games. Tatis Jr., for the record, is only 273 games into his career, and will remain stuck there until May 2023.

During the same interview in the Dominican Republic, Tatis Sr. repeatedly referred to the positive test as “minor” and said the incident could have been managed better by MLB without delving into what that meant. An educated guess at his implication: Perhaps Tatis Jr. didn’t have very high levels of clostebol in his body. Tatis Jr., the thinking might go, is having his reputation forever sullied for a clear transgression, yes, but one that didn’t materially affect his body or his potential performance.

Catlin noted that there is no lower detection threshold for steroids in sports drug testing programs.

“Any amount that is found can result in a positive,” Catlin said. “These days labs are easily capable of detecting down to low picogram levels, which is in parts per trillion. So unbelievably small amounts could have caused him to test positive.”

He offered a typical grain of salt as a comparison, which weighs 58.5 micrograms — parts per million, not trillion.

“So divide a grain of salt a million times, then divide that by 10 and that is what we can detect in urine these days in sport drug testing,” Catlin said, noting that research has highlighted this as a reason for the increased risk of inadvertent doping. “The sensitivity of the tests these days is almost unfathomable.”

Does the story about Fernando Tatis Jr. and ringworm hold water?

Beneath any discussion of the drug and how much it mattered, there’s the problem of how Tatis Jr. wound up taking it in the first place. If anything, Tatis Jr.’s admission that he accidentally used the drug while trying to treat ringworm raised more questions than it answered.

First things first: Ringworm is a fungal infection that causes an itchy, circular rash, according to the Mayo Clinic. It has nothing to do with any actual worm.

Catlin said no doctor would prescribe clostebol to treat ringworm. It’s a steroid, not an antifungal medicine. There was speculation that Tatis Jr. crafted a false excuse after finding online results related to the similarly named clobetasol, but Catlin said that drug would also exacerbate ringworm, not treat it.

Tatis Sr.’s more detailed explanation brought the Trofobol spray into the picture and more realistically explains the positive test. ESPN also reported that Tatis Jr.’s mother had posted a picture of his supposed ringworm infection on her Instagram account.

Between the further detail and the photo, we can probably move on from any idea that Tatis Jr. concocted the ringworm as a false explanation. That doesn’t mean treating it the way he did was a good idea. Catlin said Trofobol was also an “unusual product to treat ringworm” that would more commonly be used on burns. Steroids are often used to treat burns, and Trofobol combines clostebol with an antibiotic (which also wouldn’t help when dealing with a fungus).

In reading Tatis Sr.’s account, Catlin noticed that there was no mention of a doctor, and speculated that the costly error may have come in using the spray without consulting a medical professional.

“Why would he be taking a medication that wasn’t provided by a doctor? Perhaps they didn’t think twice to consider whether a spray they had could contain a banned drug and just tried it to see if it would help his condition?” Catlin said. “That I can understand.”