The #2 overall pick of the 2009 MLB Draft, Dustin Ackley entered the Mariners organization as a solid hitter without a true position. He showed the bat in the minors, hitting .280/.387/.435 in his season-plus despite being placed immediately in AA. He got settled into 2B, not exactly blowing anyone away but becoming adequate at the position. After posting a solid 117 wRC+ in his debut half-season in Seattle, the wheels fell off last season, posting a .226/.294/.328 slash line, good for a 75 wRC+.
An area of his game that has dropped off immensely is his plate discipline. After walking more than he struck out in the minors, his BB/K ratio is under 1:2 for Seattle. With the plate discipline model used in a previous post, Ackley was expected to walk about two percentage points more, which would have boosted his OBP about 15 points on its own. Using the same data for strikeouts, Ackley struck out 3.3 percentage points more than expected, making his expected BB/K ratio just over 2:3. Without any adjustments to his batted ball rates, his expected line increases to about .237/.321/.343, a wRC+ of 88.
His 2011 line was boosted by a .339 BABIP, higher than any of his three stints in the minors. He did have a high LD rate, but his LD/GB/FB profile was always right around average, so a .300 BABIP is really all one should have expected. He also does not have much power, so his 35-40% FB rate hurts his chances at hits, along with an above-average pop-up rate. With my crude regression BABIP model, it estimates a .296 BABIP for last year's batted ball profile. Combining this and the new plate discipline numbers, his line jumps to .262/.343/.368, good for a 102 wRC+, very comparable to Jason Kipnis last season.
Possibly the most surprising development so far has been his good defense. In his 2000 innings at second, he has a +9 UZR and +21 DRS. He's been especially solid with the glove, only committing six fielding errors, compared to seven throwing errors. For league-wide reference, second basemen made twice as many fielding errors as throwing errors last season. His defense and good baserunning helped provide support for his near-replacement level hitting.
While this is not the development path Seattle wanted or expected, Ackley still has a chance to be a good player. I think, along with the plate discipline, that his lack of line drives has been the biggest disappointment, leading to only 36 extra-base hits last season. If he increases the doubles and triples rate to about 40-45 a year, along with lower his FB rate to around 30%, he could be a consistent 4-WAR player for years to come.