He may not be ready to catch major league pitching yet according to general manager Brian Sabean, but Buster Posey is finally in the big leagues in 2010, according to ESPN's Buster Olney and AOL FanHouse's Ed Price. The plan is for him to play first base, which shifts Aubrey Huff to left field and allows Bengie Molina to remain behind the plate, improving the offense of a team that's ranked #23 in team TAv.
Huff's .287 TAv this year (thanks to a line of .281/.361/.450) was just average at first base, but as a left fielder, he's well above—left field currently sits at .269, meaning that Huff has more value there than at first. His weighted mean forecast was .279/.344/.463 with a TAv of .278, numbers he looks to be a little above thus far. He was already a solid option in NL-only leagues to play first, but now with impending outfield eligibility for the first time since 2007 he's a more attractive play.
The key to this whole move is Posey, of course. His weighted mean forecast heading into 2010 was .272/.348/.437, though his 80th and 90th percentiles were impressive looking numbers for a rookie: .288/.369/.480 and .297/.380/.503. Both of those lines would put him above the average at first base, but if you're playing him at catcher, his weighted mean TAv of .276 is still well ahead of the average at that position (.265).
A look at Posey's minor league numbers is enough to convince you that the top-tier projections are in the cards: the 23-year old has hit .349/.444/.552 with six homers, strikeouts in 17 percent of his at-bats and 28 walks on the season, giving him a TAv of .334 (TAv is tracked for minor leaguers as well, and translated to an MLB equivalent—to put things simply, Posey has been raking, PCL or not). [EDIT] That was Posey's untranslated TAv–the translated version is .307, which is still well above the average for a first baseman and even further ahead for a catcher.
Considering Posey was supposed to play first base all the way back in April—I drafted him in an NL-only league based on that premise, one that the Giants didn't bother following through on until just now—he may not be available in your league. Looking over the percentages though, it looks like he's available in far more leagues than he isn't—just 0.9 percent of ESPN leagues already own Posey, but 54 percent of CBS leagues already have him in their employ.