Presto! It's a platoon

I AM IN A fantasy baseball league that's so hard-core, we have a minor league player draft, and I've had Michael Choice, a former first-round pick for Oakland, stashed among my prospects for a couple of years now. Choice may not develop the power that scouts initially forecast, but last year, at age 23, he had a .390 OBP in Triple-A, and I think he'll be a fine major league hitter. So I was surprised when the A's recently traded him to Texas in a four-man deal for Craig Gentry, a career .280-hitting centerfielder. Why would Billy Beane deal Choice for a fourth outfielder?