According to numerous sources inside and outside the company, Yahoo is poised to slam dunk–I apologize, but sports puns are so easy–an acquisition of an online sports site this week.

And, predicted several of those sources, it is most likely to be San Francisco-based Citizen Sports, a maker of popular apps and games that allow fans to interact on the Apple (AAPL) iPhone and Facebook.

Interestingly, Yahoo (YHOO) CEO Carol Bartz is the keynote speaker at the high-profile sports business conference IMG World Sports Congress Wednesday morning in Los Angeles.

There is a plethora of interesting Web sports sites for Yahoo to choose from, including Yardbarker, SB Nation and Rotowire.

With Yahoo’s strong sports content business, especially in fantasy sports and news, and Bartz’s recent statements about making smaller talent and tech acquisitions–as well as the company’s recent focus on social networking and mobile integration–Citizen Sports is a perfect choice.

Citizen Sports started off in 2005 as ProTrade, an “athlete stock market entertainment company,” with $10 million from Kleiner Perkins Caufield & Byers partners Kevin Compton and Doug Mackenzie through Radar Ventures.

Other investors included Kleiner Perkins partner Will Hearst, said the Citizen Sports Web site, “as well as major sports figures, including former Dallas Cowboys quarterback and three-time Super Bowl champ Troy Aikman; Arizona Diamondbacks General Partner Jeff Moorad; legendary NFL Hall of Fame coach Bill Walsh; and Northgate Capital Venture founder Brent Jones, the former all-pro San Francisco 49ers tight end.”

But the site has morphed into an innovative digital enabler of interaction among fans of all kinds of sports, via its fantasy sports games and Sportacular iPhone app, as well as numerous apps on Facebook.

It also has tight relationships with Sports Illustrated magazine and other sports partners.

Most interesting is that one of its co-founders, Jeff Ma, was one of the members of the infamous MIT blackjack team, made famous in the book, “Bringing Down the House” and the film, “21.”

It is unclear how much Citizen Sports would sell for, but estimates put its price at about $40 to $50 million.

Both Citizen Sports and Yahoo declined to comment.