I think you follow the line of looking at what he'd get on the open market; something around 1/17, 2/30, maybe taking a little home town discount; 1/15, 2/28 perhaps, absorbing the extra year and adding a few million to next season as a good will gesture, maybe something around Sizemore's 6mil and if he's so inclined, spreading the money over the length of the contract coming out at 2/21 or 3/34 including 2015.
And if that doesn't do it, the trade option should yield a decent return considering his salary. That said I think he qualifies as a 10-5 guy this season, unless the DL season doesn't count against that.