I've broken out the extensive discussion of potential second basemen into its own Clubhouse thread. What has been said is that Garcia is the incumbent but not a lock. There's at least 5 or 6 possibilities - Garcia, Nunez, Baker, Lipscomb, Vargas, and Alu. None are blow you away guys yet.
Garcia may be the default, and, to his credit, has shown above average contact skills. Can always count on him for a groundball :~
Nunez is a Rule 5 guy who has shown nothing offensively in the minors but is easily the best fielder. There's an incentive to keep him around at least as an MI backup.
Baker is a lower round draftee who has probably outdone his draft day projections to work himself into the mix. Oddly, he's older than Garcia at the point. Plays decent 2d base defense, has hit for average, but has shown no power in the minors.
Lipscomb advanced 2 levels last year and held his own playing multiple positions. System defensive player of the year. Good ISO, not much in terms of OBP. Looks like he may have a career as a utility infielder but probably will begin at AA/AAA.
Alu is another multi-position guy on the 40 man roster with options. Has hit at times in the minors, didn't look bad when playing 2nd while Garcia was in the minors, but is a bit older now and looks like organizational depth.
Vargas - last year's Every Day, Every Play guy has a job while the minors guys develop and was a roster default starter when the likes of Kieboom and Garcia failed.