After a season of replacement referees, botched calls and lockout-driven controversy, several NFL officials remain deeply upset about the grading system used to choose the referee for the Super Bowl.

"You see grades being changed, constantly being changed, only for certain people," one official told Yahoo! Sports.

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"It's disheartening," said another official, "and you never think at this level that would happen. It's the individuals running the show that have created this mess. If you talk to 121 guys, there will be 100-plus who say the system is horrendous."

At issue is an allegation that the NFL selects who will referee the Super Bowl based on favoritism, not solely on merit. This leads to Jerome Boger, the NFL's presumed selection to referee Super Bowl XLVII on Feb. 3. On Monday, the website footballzebras.com reported that Boger received eight downgrades during the 2012 season and all eight were reversed. Multiple sources with knowledge of the grading system made the same claim to Yahoo! Sports.

Though officials who spoke to Yahoo! Sports say Boger is far from the worst official in the game, they question his assignment to this year's Super Bowl.

"[Boger] shouldn't even be eligible for the game," one said. "Everybody basically knows what's happening. You see when grades appear, and when grades mysteriously disappear. Any incorrect call or missed call will disappear for no reason at all."

Asked about this, Michael Signora, vice president of the NFL communications department, wrote in an email to Yahoo! Sports: "There is no merit to the suggestion that Jerome Boger's grades were treated differently from those of any other official."

Signora continued: "Every official has the opportunity to have preliminary grades reviewed, and no downgrade is removed unless there is a consensus among the supervisors to do so, and without the approval of the head of the department. Fourteen of our 18 referees had grades modified in the course of the review process."

Signora called the anonymous claims "inaccurate and unfair."

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The larger issue, according to the officials, is a system that many feel is flawed. Officials are graded after each game by a group of retired referees. Any downgrades or "dings" for mistakes during the game can be appealed by an official, and are then reviewed by supervisors and the league. Mistakes made in games can be altered or erased by the league with no explanation. Officials are overseen by Ray Anderson, the NFL's vice president of football operations, who has been at his position since Roger Goodell promoted him after becoming commissioner in 2006. Requests for an interview with Anderson were declined.

Officials told Yahoo! Sports the mystery of league decisions adds to resentment among their peers. "It takes the integrity away from the process," said one official who, like the others, commented anonymously out of fear of repercussion from the league. One even said the referees at their annual preseason clinic try to predict who will be chosen for the Super Bowl, even though that assignment is supposed to be based on a season's worth of games.

"Before one snap, you may already know who four of the seven Super Bowl refs are," said one. "Who they favor and who might be next. Some guys are Teflon, other guys are Velcro."

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