National League Most Valuable Player Ryan Braun has won his appeal in a first-ever overturning of a likely 50-game doping suspension, the Major League Baseball Players Association said on Thursday.

Major League Baseball issued a statement saying it “vehemently disagrees” with the decision, which is the first known case of a major league player overturning a looming drugs ban.

“Under the Joint Drug Agreement, a player’s successful challenge to a suspension normally would not have been made public,” the players’ union said in a statement.

“The parties have agreed, given the particulars of this case, that an announcement is appropriate.”

Baseball’s anti-doping procedures call for drug testing and the appeals process to be confidential, but Braun’s positive test for a performance-enhancing drug was reported in December by ESPN, when he issued a statement through a spokesman to ESPN that he expected to be “exonerated”.

However, baseball officials made it clear they disagreed with the decision.

“As a part of our drug testing program, the Commissioner’s Office and the Players Association agreed to a neutral third party review for instances that are under dispute,” MLB executive vice president for labour relations Rob Manfred said in a statement posted on MLB.com.

“While we have always respected that process, Major League Baseball vehemently disagrees with the decision rendered today by arbitrator Shyam Das.”

Das’s vote gave Braun a 2-1 ruling by a panel of three arbitrators, MLB.com reported.

The Milwaukee Journal-Sentinel reported that the appeal went in Braun’s favour because of “some kind of technicality” in the test conducted last October.

On November 22, Braun had been named MVP of the National League for his role in helping the Milwaukee Brewers claim their first division title in almost 30 years.

His outstanding season came after he inked a five-year contract extension through 2020 worth $US105 million last April.