A quick point: Pete Kozma and Ryan Jackson shared shortstop duties at Triple-A Memphis last year. Actually, that's not quite right. Jackson played 102 games at short and Kozma played 45, which tells you who the Cardinals thought was the better shortstop. The numbers back up the belief that Jackson is the superior fielder, as he made 4.18 plays per game at Memphis, Kozma 3.02. Jackson had a better fielding percentage and turned a higher percentage of double plays. Jackson even hit better -- .272/.334/.396 versus Kozma's .232/.292/.355. In fact, Kozma played poorly enough at Memphis that the Cardinals have admitted they nearly removed him from the 40-man roster last summer.
Of course, Kozma got the call when Furcal was injured last September and hit surprisingly well (.333/.383/.569). He then delivered a couple big hits in the postseason, although if you remember his defense was very shaky, and not just on that infield fly pop-up to shallow left against the Braves in the wild-card game.
Look, Jackson is the better player. Kozma isn't anything close to a .300 hitter and I don't see the evidence that he has the ability to play shortstop in the big leagues on a regular basis. He may win the job out of spring training based on September's performance, but I think Jackson eventually takes over.