Lynn Henning of the Detroit News expects the Tigers to make a trade before the regular season, "perhaps a big one." Henning writes that the team could trade away starting pitching if Nate Robertson and Dontrelle Willis are healthy. Henning also mentions Marcus Thames and Ryan Raburn as possible trade candidates.
Willis and Robertson each have considerable negative trade value, as they'll both make at least $7MM in 2009 and 2010. Unless the Tigers are willing to pay most of that, they'd have to trade one of their other starters: Justin Verlander, Jeremy Bonderman, Armando Galarraga, Edwin Jackson or Zach Miner. Trading one of those starters would leave the Tigers with a thin rotation.
The Tigers don't have a starting spot for Thames if Gary Sheffield stays healthy.