The signing of the former highly rated prospect, now 29, is very ironic in one regard: McPherson missed the entire 2009 season, as he had 2007, with back problems. One reason the A's are searching for third-base help is their long-time mainstay at the position, Eric Chavez, has for years battled his own back problems and underwent yet another operation on June 23.McPherson also had an operation on his back in July. His agent, Matt Sosnick, told ESPN.com that McPherson is "already working out. He's 100 percent." Rated the Angels' No. 2 prospect by Baseball America in 2005, McPherson has slugged 150 homers in 608 Minor League games but has only compiled 371 big league at-bats. In them, he has 18 home runs and 126 strikeouts.