Yahoo! Sports announced Monday that it has partnered with MLB Advanced Media to make its commissioner product the “official fantasy baseball game of MLB.com” for 2010.

The deal includes a bit more than one that might make a brand the official underwear of the Chik-Fil-A Bowl. The co-branding agreement positions Yahoo! 2010 baseball as the primary fantasy offering on MLB.com’s fantasy homepage. MLB’s own suite of fantasy games remains, but you won’t find (at least as of Monday afternoon) offerings from past partners such as ESPN or ProTrade.

Aside from the nice-looking “official” tag, partnering with MLB.com provides attractive traffic numbers. Although FSB.com doesn’t have specifics for each company’s subdomains, this quick snapshot of the past year shows MLB.com carrying an audience of about 5 million to 7 million in the buildup to baseball season before jumping to 12 million in April. For comparison’s sake, that represented significantly more unique users per month than (multi-sport) Web heavies ESPN.com and CBSSports.com over the same span.

Beyond the positioning on MLB.com, the partnership also brings to Yahoo! customized player highlights that users can subscribe to for the season for $9.95. The package will offer in-game and post-game highlights of players on your fantasy team and will be available for free preview to Yahoo! fantasy players for the season’s first two weeks.

“We believe this product will exceed fantasy baseball players’ growing appetites for deeper engagement by delivering an immediate, high-quality experience,” MLB.com senior VP of business development Kenny Gersh said in the release.

This marks Yahoo!’s third fantasy partnership with an American professional sporting body. Previous deals made the most-trafficked fantasy outlet the “official” provider of fantasy golf for PGA.com and fantasy hockey for NHL.com.

FSB.com has learned that KFFL and RotoExperts have reached a syndication agreement that will put RotoExperts content on KFFL for three fantasy sports: NASCAR, soccer and golf.

Fantasy racing folks can now find RotoExperts branded sections on KFFL’s NASCAR home page: Picks and Points, Nationwide Series and Race Recap. Basically, RotoExperts will be providing race preview and wrap-ups for the Sprint Cup series, along with content for the lower-division Nationwide races.

Scott Engel of RotoExperts tells us that his site will also supply KFFL with weekly previews and reviews of English Premiership socceer action and similar weekly coverage of PGA events. There is currently no set ending point for the agreement between the fantasy content sites.

KFFL and RotoExperts each reside within Fantasy Sports Ventures’ Fantasy Players Network. Along with KFFL, Yahoo!, NFL.com, SI.com and USA Today Sports Weekly also syndicate RotoExperts material.