Ryan Braun, the 2011 National League Most Valuable player and the cornerstone of the Milwaukee Brewers' franchise, tested positive for a performance-enhancing drug and could face a 50-game suspension to begin 2012, a blow for the Brewers and a sport that seemed to put the worst of its steroid era behind it.

GALLERY: Ryan Braun

Braun, however, plans a vigorous defense of the positive test. He will appeal any suspension and on Saturday night told USA TODAY of the result: "It's BS."

ESPN first reported that Braun had tested positive, and that he'd provided a urine sample during the 2011 playoffs, then was informed of the positive result in late October. A source told ESPN the positive result came about from elevated levels of testosterone in Braun's system, and a subsequent test revealed the testosterone was synthetic.

Braun, 28, who was aware of ESPN's forthcoming report, issued a statement via his agency:

"There are highly unusual circumstances surrounding this case which will support Ryan's complete innocence and demonstrate 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 he will ultimately be exonerated."

Braun topped the Dodgers' Matt Kemp in NL MVP balloting, after he hit .332 with 33 homers and 111 RBI. During the season, the Brewers signed Braun to a five-year, $105 million extension that would keep him in Milwaukee through 2020.

In his first five major league seasons, Braun has averaged 36 homers, 118 RBI and a .563 slugging percentage.

He becomes the first reigning MVP to test positive for performance-enhancing drugs, though many award-winners through the early part of this century -- Barry Bonds, Roger Clemens, Alex Rodriguez and Jason Giambi, to name a few -- either tested positive for steroids or were strongly linked to them through legal proceedings or investigations.

Other than Los Angeles Dodger slugger Manny Ramirez's first performance-enhancing drug ban, in early 2009, baseball's drug suspensions had been limited largely to fringe players since the sport tightened its PED policy after the 2005 season.

Ramirez, in fact, was the lone player on an active major league roster suspended during the 2011 season.

In the wake of slugger Mark McGwire's January 2010 admission that he used performance-enhancing drugs, Commissioner Bud Selig all but declared the game's steroid era over in a statement:

"The use of steroids and amphetamines amongst today's players has greatly subsided and is virtually nonexistent, as our testing results have shown. The so-called steroid era — a reference that is resented by the many players who played in that era and never touched the substances — is clearly a thing of the past, and Mark's admission today is another step in the right direction."

If Braun's result is upheld, the sport's cleaner image will certainly be sullied anew.

Braun is a charismatic star, respected by teammates and foes alike, and he is close friends with Green Bay Packers quarterback Aaron Rodgers. As word of Braun's test spread, the game seemed it was bracing for another of its stars to be sullied.

Tweeted Phillies shortstop Jimmy Rollins: I really hope Braunie's initial test is not upheld........

However, it's not publicly known if any player suspended under MLB's drug policy has had a positive test result overturned.

Brewers owner Mark Attanasio, whose club said it had not been contacted by the commissioner's office regarding a test result, released a statement Saturday night: