As an icon of Green Bay, Wis., where the beloved Packers are darn-near worshipped, Favre blemished his legacy by continuously waffling on a return after a tear-filled retirement and then forcing a trade away from the team to the New York Jets.
"How could he don the jersey of anything non-Packer?" said the fans in disbelief.
Oh, but wait, it gets better. His leaving was just a warm-up to an act deemed traitorous of an unprecedented measure -- retiring yet again before changing his mind and maneuvering his way to the Pack's biggest rival, the Minnesota Vikings. Is nothing sacred?
Like many hometown fans, Packer Backers wished their athletes would treat the game as they do, with loyalty, rather than as just business or a personal ambition.
This is what Favre is guilty of. He wanted to play ball -- jerseys be damned -- and "tarnished" his legacy in the eyes of Packer fans with every post-Packers move.
No. 2: Wade Boggs/Roger Clemens/Johnny Damon
Wade Boggs, Roger Clemens and Johnny Damon all committed a big no-no: starring for years for the Boston Red Sox and then going to the hated rival New York Yankees.
To many, they solidified the notion that athletes only care about money. As Damon said in '05, "There's no way I can go play for the Yankees ... It's definitely not the most important thing to go out there for the top dollar." Guess what? Seven months later, he went for top dollar, turning down an offer from the Red Sox in favor of a four-year deal with New York.
Clemens initially left Boston for another division rival, Toronto. Two years later, he was traded to New York, where he helped the Yankees win two more titles in four World Series appearances.
Of course, Clemens also has the whole perjury and steroid scandal thing over his head, which baseball fans the world over may put in the category of traitorous.
No. 1: LeBron James
LeBron James went to new heights to declare his controversial intentions.
Playing in Cleveland, James was King. His statistics were often head-shakingly high. And as James was born in nearby Akron, Ohio, the old idea of player loyalty was even more so embedded in the Cavalier fans.
All of this came crashing down on July 8, 2010, with "The Decision." During a live TV special, James made his free agent destination known with the infamous words, "I am taking my talents to South Beach."
He got criticism for the self-aggrandizement, let alone his decision to play for the Miami Heat with other big-name free agents. Factor in his scant notification to the other suitors, including his Cavs, and we have ourselves a wonderfully news-making traitor story.
Just ask Cavaliers owner, Dan Gilbert, whose scathing (and funny) letter to fans described the leaving LeBron in non-flattering terms.
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