After being originally drafted back in 1997, McDonald was added to the Orioles 40-man roster for the first time in November, 2002. McDonald was then optioned in both 2003 and 2004 (spending some time in the bigs with the Orioles in 2004). He was outrighted to the minors and became a minor league free agent in the off-season between 04 and 05, and since that time has not been back on a 40-man roster, playing on a series of minor league contracts.
So, my conclusion is that McDonald has one option left. That means that the Twins can keep him around if they want to by optioning him to the minors when Cuddyer comes off of the DL (or sooner, if they need the roster spot for something else -- like Rondell White's return, for instance).
I've been absent for the last day and a half due to moving and blogger issues, but should have a right up for today's game sometime this afternoon.