The Twins are looking for a starting third baseman. What that means for Plouffe is unclear, but could entail him moving back to the outfield. It's also possible they come up with a left-handed bat platoon-type option.
That would seem to contradict what Ryan said in his 2013 Offseason Handbook interview:
"(Plouffe is) coming in as the third baseman. Yes, he will. I need to create some competition over there though. And we will. And he’s aware of that. Nothing wrong with competition."
I won't believe they'll sign anyone to replace Plouffe until I see it. I could see them adding a left-handed option. (St. Paul's Jack Hannahan?) But of the problems the Twins needs to address, this needs to be towards the bottom of the list.