ESPN and Major League Baseball have scheduled a mid-day announcement that will reveal the extension of their TV rights deal through 2021, at an average annual rate that essentially doubles their existing arrangement.

Sources say that the new deal will pay MLB $5.6 billion for eight years, an average of $700 million per year, for domestic rights to content including weekly Sunday, Monday and Wednesday games, a wild-card playoff game, highlights for ”Baseball Tonight” and additional digital, international and radio rights. Highlights of the extension include fewer blackouts, more games on existing nights on ESPN’s schedule and more dedicated studio hours to baseball.

The new contract folds together four separate deals involving TV, digital, radio and international that added up to an average of $350 million per year.

Sports Business Daily first reported news of the pending extension.

The contract is not the last windfall Major League Baseball figures to earn in the coming months. Packages with Fox ($257 million per year) and TBS ($149 million) also are up for renewal or bidding by the end of 2013.