ATLANTA (Reuters) - The decision by Atlanta Falcons quarterback Michael Vick to plead guilty to dog fighting charges is one more blow to American sports fans after a summer in which three US sports have been tainted by scandal.

Vick, one of the NFL's most dynamic players, says he will formally plead guilty on Monday to federal charges that he helped run an interstate dog-fighting enterprise known as "Bad Newz Kennels" from 2001 through April 2007.

His case has polarised fans torn between revulsion at the crime, shock at his sudden fall from grace and and sympathy for a man who was idolised as much for his celebrity and wealth as his ability.

"I'm a huge dog lover and a huge football fan," said Tim Hemans at an Atlanta sports bar. "I think justice should be served and he should go to jail.

"I don't care whether he is a football player, whether he is black or white. He participated in an incredibly cruel sport.

"I am embarrassed as someone who lives in Atlanta that he is associated with our city," added Hemans, referring to the 27-year-old's role as the public face of the Falcons team.

Imam Robinson, a college student, had sympathy for Vick: "He shouldn't go to jail. They shouldn't make an example of him. If he wasn't famous he wouldn't be going to jail."

During the US summer, the baseball season is in full swing while football and basketball teams trade and draft players ahead of their first games.

Each of those sports, however, has been overshadowed by controversies that have raised questions about the price of success.

August 7 will go down as the night Barry Bonds of the San Francisco Giants slugged the 756th home run of his baseball career, breaking a record held by Hank Aaron for 33 years.

Bonds' achievement was compromised by suspicion that he may not have spoken truthfully when denying that he used steroids to boost his career, according to many fans.

One week later, former National Basketball Association referee Tim Donaghy pleaded guilty to two felony charges and admitted to providing tips on games he officiated to professional gamblers.

Donaghy, 40, faces a maximum prison sentence of 25 years but stands to be sentenced to less time as part of a plea deal with federal prosecutors.

Vick had initially denied involvement in pit bull fights that an indictment said took place on his property in Virginia. He then accepted the deal after associates agreed to cooperate with prosecutors under their own plea deals.

Prosecutors charged that dogs sometimes fought to the death and some losing or underperforming dogs had been shot, drowned, hanged, electrocuted or killed by being slammed to the ground.

At the root of the problems faced by celebrities such as Vick who disappoint the public were the pressure they face and the inflated hopes invested in them by fans, said Earl Ofari Hutchinson, author of books on race and politics.

"The expectations that we put on celebrities and sports icons are phony, unfair and hypocritical....We put these people on an inflated pedestal and when they tumble the wrath of the society comes down on them," he said.

Fans were divided on whether he should be allowed to play for the Falcons again and many said they were bewildered that Vick, who earned a multi-million dollar salary as well as commercial endorsements, should risk it all for dog fighting.

At the same time, several fans said Vick deserved a second chance once he had been through the legal process.

"I don't think he should be over-penalised because of who he is," said civil rights leader Al Sharpton on his radio phone-in show in a view echoed by many callers.

"He should be treated as any first offender. You can't treat someone different because they are a celebrity."