With all of Khalil's problems at the plate, the one thing that was generally agreed upon was that he'd always be a magnificent defensive shortstop.  That didn't turn out to be true as his personal problems seem to have corroded his defensive skills. 

While moving to third may put less importance on his defensive  "timing issues", I would suspect there would be even more pressure on him to hit for power.

I hope that someone is really watching over Khalil because a lot of people are very concerned about his well being off the field.

• Hacksaw: Khalil Greene’s anxiety disorder alarming
  "The story is not just about a deepening slump or errors in the field. It is about the mental makeup and the well-being of a player we all knew and most of us liked. It is a scary story of a darker side few knew existed that has now taken a turn for the worse. I was upset to hear there had been more injuries and more violent outbursts, some in front of teammates and others in private. It was alarming."

• Hacksaw: Khalil Greene update; moving to 3rd
  "The ex-shortstop has agreed to move to third base, while extending his rehab assignment with the Cardinals minor league affiliate Memphis in the International League."

• Greene making move to third base | MLB.com: News
  "We're getting excellent shortstop play, so this allows him to. ... He's got to have some timing issues playing short, and there's less that you have to be concerned about playing third base."