Fox Sports has emerged as the top rival to CBS on the NFL's Thursday night package.

CBS has had the rights for the past two seasons.

The bidding is expected to substantially exceed the estimated $300 million that CBS currently pays for the telecasts.

The NFL outlined a one-year deal with another year at the league's option, and also outlined a separate request for proposals to simulcast the games online. 

CBS, the country's most-watched network, averaged 13 million viewers for the Thursday games, a 6% increase over 2014, the company said recently.