Last season, Scott Sizemore finally got a chance to play.

He had to get traded to get a chance to play, but the Tigers did trade him to the A's, who shifted him from second base to third base. And Sizemore did well, hitting in the majors like he'd once hit in the minors. In 93 games with Oakland, he posted a 113 OPS+ and it looked like the Athletics had their Third Baseman of the Future.

Well, the Future isn't Now. Monday evening, the A's announced that Sizemore has torn the anterior cruciate ligament (ACL) in his left knee and will miss the entire 2012 season.

In Sizemore's absence, the top candidate for regular third-base duties is utility infielder Adam Rosales, who spent much of last season on the Disabled List and much with triple-A Sacramento, but did good work as a reserve with the A's in 2010. Unfortunately, the club doesn't have a third-base prospect who's even remotely ready to step in and replace Sizemore's production. Or even Rosales's, probably.

Update: Upon further review, it seems the A's are considering prospect Josh Donaldson as Sizemore's replacement. A sandwich draft pick five years ago, Donaldson's been mostly a catcher in the minors but did play some third base with Sacramento last season. John Sickels rates him a C+ prospect; Baseball America ranked him this winter as the organization's 20th-best prospect. The odds are obviously against him, but the club might be desperate.