NEW YORK -- Major League Baseball agreed with Fox and Turner Sports on eight-year contracts that will run through 2021 and keep the World Series on Fox.

The amount baseball receives from the two networks will double to an average of about $800 million annually, with Fox's share averaging about $500 million.

"Both networks are passionate about baseball and are committed to covering, promoting and growing the sport, and I want to thank them for their continued support," commissioner Bud Selig said Tuesday.

Fox also will retain rights to the All-Star Game and a league championship series every year, and adds coverage of two division series starting in 2014. Fox broadcast the World Series in 1996 and 1998, and has had exclusive rights in 2000.

TBS will retain the rights to air one league championship series, two division series and one wild-card game.

MLB Network will continue to have the right to two games from one division series in the new eight-year deal.

Fox and TBS will alternate between showing the American League and National League playoffs from year to year. MLB Network's two division series game will come from Fox's games.

ESPN and MLB in August announced a new deal covering 2014-21 that, according to reports, will increase ESPN's average yearly payment from about $360 million to approximately $700 million.

Fox, which broadcasts a Saturday regular-season game each week under its current deal, will double regular-season game rights from 26 to 52 under the new contract. Twelve of those will be exclusively shown on Fox, but the deal gives the network the right to air as many as 40 games on another nationally distributed Fox channel.

"We are continuing to evaluate the possibility of a national sports channel," Randy Freer, co-president of Fox Sports Media Group, said during a conference call. He added that no announcement on such a network was imminent.

Speculation has been that Fox will rebrand its Speed Network into an ESPN-style, all-sports network, and having major league baseball games to show on it would help greatly with distribution to cable and satellite providers.

Under the new deals, TBS also will have the rights to air 13 regular-season Sunday games. However, it will gain more telecasts that will be broadcast simultaneously with the local club TV feed within a market and increased digital rights.

Turner had carried all four division series from 2007 through last year but gave up two division series games to the MLB Network under a deal running through 2013. That was part of a financial agreement that gave it rights to the two wild-card round games this year.

ESPN gains a wild-card game starting in 2014. It also had televised 26 Sunday games each season.

Information from The Associated Press was used in this report.