All things considered, Kolten Wong had a solid, but not spectacular second full season with the St. Louis Cardinals. Offensively, the 25-year-old second baseman put up first-half numbers (.280/.343/.434, 114 wRC+) worthy of All-Star Game consideration. Unfortunately, Wong's production fell off considerably after the All-Star break, and this is likely due to a combination of fatigue associated with a 162-game MLB season and opposing pitchers making progressive adjustments against his strengths.
Despite being just over 1,100 plate appearances into his MLB career, Wong is already known for being an aggressive hitter (5.4% walk rate), and for the most part, it works for him. As a second baseman, Wong can afford to be a league average hitter (with above-average positional power) while still providing a considerable amount of value to the Cardinals, considering his above-average ability on defense and on the bases.
That being said, when the Cardinals selected Wong in the first round of the 2011 draft, they projected the University of Hawaii product as more than just a league average hitter. Given the aging core (Adam Wainwright, Matt Holliday, Yadier Molina, Jhonny Peralta), the front office of the Cardinals will look to Wong as a key cog in the team's next core (along with Stephen Piscotty, Randal Grichuk, the pitchers, and hopefully Jason Heyward).
A starting point for Wong in becoming a better, more consistent hitter is developing a more patient, selective approach, particularly with two strikes in the count. Of course, strike zones currently implemented by umpires are bigger than the rule book zone, but this still should not negatively affect what Wong is trying to do at the plate. Just ask Matt Carpenter, who, despite being the "poster child" of dealing with umpires' zones, has maintained and executed his plan of action at the plate in each of the last three seasons.
Wong's performance with two strikes in 2015
On the surface, these numbers do not appear very good (and they're not, really), but Wong's performance is actually better than league average, as the league's two-strike slash line was .177/.244/.272 in 2015. However, Wong's attainment of decent results should not be used to hide the presence of a clearly-flawed process. As you can see in the graph below, Wong swung at pitches outside of the strike zone with two strikes more than any other Cardinal hitter last season.
When collecting data for this graph, I started with Wong and worked my way down the 2015 Cardinals roster one-by-one, anticipating at least one Cardinal with a higher out-of-zone swing rate than Wong. Yet, I didn't find one, and this includes names (i.e. Pete Kozma, Tony Cruz, Jon Jay, Peter Bourjos, etc.) that I was unable to include on an already-crowded graph.
Wong's above-average performance when expanding the zone is impressive and is a testament to his plate coverage (and beyond). However, in order for Wong to become a next-level hitter, similar to the one many expected after seeing his continued success in the minor leagues, he needs to develop a more patient plate approach. Now, there is a possible problem here, though. Is Wong's expansion of the zone purely an aggressiveness problem or could it possibly be a pitch recognition problem? If the latter is involved (even minimally), we may be dealing with a low walks hitter that is prone to streakiness for the entirety of his career. Again, as I stated earlier, Wong will almost certainly still be a valuable player, but it will remain to be seen as to whether or not he should be reasonably considered a component of the team's next "core."