On Tuesday morning, MLB Players Association executive director Michael Weiner issued a statement in Braun's defense, advising against a rush to judgment.
"Our Joint Drug Agreement is designed to protect a player from a rush to judgment before he can challenge a reported positive test result," the statement read. "Fairness dictates that Ryan Braun be treated no differently. I urge all to reserve judgment on this matter until the JDA's process has played itself out."
According to sources cited in the ESPN.com report, Braun submitted a urine test during the playoffs in October that showed a level of testosterone high enough to trigger a positive test. A second test on the sample revealed that the testosterone was exogenous, or from outside Braun's body, meaning it was generated by a synthetic substance.
FOX's Ken Rosenthal also offered a different account via Twitter on Sunday.
"What he did triggered violation of #MLB steroid-testing policy," Rosenthal wrote. "Source says substance was prohibited, but not PED."
The positive result has Braun facing the requisite 50-game suspension for his first violation of the Joint Drug Prevention and Treatment Policy if the initial finding stands, but the positive test has not been announced because Braun is appealing the finding through an arbitration process.
A source close to Braun told ESPN.com that the outfielder immediately requested a second test after learning of the results. The source said the second test result was not positive.
Braun responded to the test result by telling MLB.com's Adam McCalvy in a text message: "I would love to talk, but unfortunately I'm not really allowed to say anything right now. My day will come soon, though."
Officials from Major League Baseball and the MLB Players' Association have not commented on the report.
A spokesman for Braun released the following statement on Saturday: "There are highly unusual circumstances surrounding this case which will support Ryan's complete innocence and demonstrate that there was absolutely no intentional violation of the program. While Ryan has impeccable character and no previous history, unfortunately, because of the process we have to maintain confidentiality and are not able to discuss it any further, but we are confident that he will ultimately be exonerated."
Braun told USA TODAY of the test result, "It's B.S."
In a statement released Saturday night, Brewers owner Mark Attanasio said the club had not been contacted by MLB about the test results. He stressed that the appeal process must play out before there is a rush to judgment.
"Ryan Braun has been a model citizen in every sense of the word, both in the Milwaukee community and for the Brewers. Since joining our organization in 2005, he has been a person of character and integrity," Attanasio said in the statement.
"MLB has put a confidential testing program into place, which I personally support, that has a specific review process that must be followed before determining whether a player is in violation. Ryan has issued a statement that there are highly unusual circumstances surrounding this case that will support his complete innocence and demonstrate that there was absolutely no intentional violation of the program. We are dealing with an incomplete set of facts and speculation. Before there is a rush to judgment, Ryan deserves the right to be heard. We are committed to supporting Ryan to get to the truth of what happened in this unfortunate situation.
"As a father, I take the use of prohibited substances seriously, because I know the effects they can have on the body and on a person's life. I want the Milwaukee community to know that we support drug testing not only because it is MLB policy but because it is the right thing to do.
"I need to acknowledge that at this point the Milwaukee Brewers have not heard from the Office of the Commissioner or any official entity related to the MLB testing programs. Accordingly we do not have access to any of the facts or knowledge of any of the circumstances that are being circulated in the media with regard to Ryan Braun. The team will release follow-up statements at the appropriate time."
Braun, 28, helped lead the Brewers to a franchise-record 96 wins in the regular season and the NL Central title, their first since moving to the NL in 1998 and Milwaukee's first division title overall since 1982. He hit .332 with 33 home runs, 111 RBIs and 33 stolen bases to hold off the Dodgers' Matt Kemp in the MVP vote.
A first-round pick of the Brewers in 2005, Braun has hit .312 with 161 homers and 531 RBIs in five seasons, winning Rookie of the Year honors in 2007 and racking up four All-Star appearances and four Silver Slugger Awards.