Last year, Guillen was the shortstop. He started out this year at first base and later moved to third base. Could his next move be to left field? He has been working out there and Jim Leyland says that it's possible he could play out there eventually. He is trying to think of a way to have Brandon Inge play third base more often which I think is a good thing. Moving Guillen to left field doesn't seem like the best solution though. Carlos has never played the outfield before and his reactions to infield plays over the last couple of years does not give me much confidence that he will play well anywhere defensively.
My solution would be to give up on Gary Sheffield and move Guillen to designated hitter. As with the Willis/Galarraga move however, not every move is purely a baseball decision. Guillen is a veteran team leader who doesn't want to be designated hitter so it's difficult for Leyland to just pencil him into that slot even though it seems the logical thing to do. It's also difficult for the Tigers to give up on Sheffield who is owed a lot of money this year and next year.
For now, Marcus Thames is the regular left fielder but I suspect another shake up will happen once he stops hitting for a few games. I do have to give Leyland credit for one thing this year. He is not sitting on his hands waiting for things to happen. He is restricted by economics and politics but he's trying to do something even if it doesn't always make sense on the surface.