It's "game on" for Carrie Underwood -- not on a football field, but in court.

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The country music star has sung the opening theme song to NBC's "Sunday Night Football" since 2013, with the network unveiling a new version of the song, called "Game On," in 2018, The Washington Post reported. Underwood, along with her producer, Mark Bright, the National Football League and NBC, were sued in a Manhattan federal court Wednesday by singer Heidi Merrill. who claims Underwood's song is "substantially — even strikingly — similar, if not identical" to a song written by Merrill with the same title.

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Merrill claims she pitched the song, which she posted to YouTube in March 2017, as a possible theme song to Underwood, Billboard reported. According to the lawsuit, filed in U.S. District Court for the Southern District of New York, Bright said through an assistant that he'd "have to pass," Billboard reported.

Also named as co-defendants in the lawsuit are music publishers Sony Corp. and Warner Music Group, the Post reported.

According to the lawsuit, "The defendants knowingly, willfully, and intentionally copied original, copyrightable elements of the plaintiffs’ original Work," the complaint continues, "publicly performed or displayed the Infringing song, and otherwise violated the plaintiffs’ exclusive copyrights in the work for substantial personal and commercial gain."

Here is Merrill's version of "Game On":

And here is "Game On," sung by Underwood:

The lawsuit seeks unspecified damages to be determined at a trial, according to CNN.

The NFL declined comment, the Post reported. A spokesman for NBC said the network does not comment on pending litigation, the newspaper reported. A representative for Underwood has not responded for a request for comment, Billboard reported.