The NFL Referees Association reportedly has a problem with Shannon Eastin officiating an NFL game, and it has nothing to do with the fact that she's a woman.

The union said that it would question her credentials because she had participated in the World Series of Poker, profootballtalk.com reported on Thursday. The league, though, has vetted and accepted Eastin, who will become the first woman to officiate an NFL game Thursday night when the Chargers play the Packers in San Diego (ESPN, 8 p.m. ET).

"The NFL does extensive background checks on prospective officials, including the current group of replacement officials," NFL spokesman Michael Signora said, according to the website. "All of them have passed the NFL's rigorous screening process, including Shannon Eastin. Past participation in an event such as a poker tournament does not disqualify a person from consideration as an NFL game official."

The league is using replacement officials after not being able to reach a new labor agreement with its referees.

Per the NFL's rules on gambling and officials, Signora did say that if Eastin became a regular official she would not be allowed to take part "in a professional gambling event, such as the World Series of Poker, at any time of the year."

Eastin, 42, has been an official at the NCAA Division I-AA for four years. She's also a world-class athlete, having earned six national judo championships.

Eastin will be the line judge for the Chargers-Packers preseason game.