With only 3 keepers there are going to be a LOT of good players to re-draft and 3B is pretty deep this year. Wouldn't be surprised if you can't get the most underrated 3B -- and one of the best -- back in Aramis Ramariz. If not you could add another Sox in Will Middlebrooks or go with the suddenly red hot Chase Headley or hope for a bounce back year with Brett Lawrie on the new, improved Jays line-up.
Main thing to keep in mind with keepers is to NOT make a decision just thinking about your team. Look over the rosters of your opponents. If it is a Yahoo league go to your "trophy" page and click on your old roster and all the other rosters are still there too to access. Try to guess who you think these other guys will keep and look over the possibilities you can get in your re-draft. For example if someone has say Trout, Posey and Votto as well as Headley they aren't likely to keep Chase as one of their three.