By all accounts, Dustin Ackley has not lived up to the expectations that come with being the second overall pick in the draft. The UNC product—who Baseball America said "has the best pure swing and pure bat in the '09 draft class, and maybe the best this decade" prior to the 2009 Draft—was expected to be an impact bat for the offense-starved Seattle Mariners for years to come.
As often is the case with prospects, hype and reality end up being two very different things. Despite having a .293/.399/.451 slash line in the minors, Ackley struggled for the most part once he reached the big leagues. His disappointing tenure in Seattle led to last summer's trade to the Yankees at the deadline, where Ackley caught fire once he returned from the disabled list in September. His .288/.333/.654 line, four home runs, eleven RBI and Mike Trout-like 161 wRC+ was much-needed at a time when the Yankees' offense was struggling to score runs.
Given his very recent history, few viewed his September surge as any more than a passing hot streak (as evidence by ZiPS' much more reasonable .253/.310/.415, 97 wRC+ projection for him in 2016). However, there do seem to be reasons to expect a version of Ackley closer to his 23-game cameo with the Yankees in 2015 than the version that struggled in Seattle.
One reason to be hopeful Ackley's continued offensive success is his batting stance. In a story for NJ Advance Media, Ackley credits the Yankees' hitting coaches last season—Jeff Pentland and Alan Cockrell—for helping him settle his down his stance.
The left-handed swinging Ackley, who's had injuries to his left foot, said he has a tendency to come off that back foot too soon when swinging in the box, and worked on staying more grounded.
'It's something that I really have to focus on," he said. "You want to go to the ball and it's almost like, you're going to the ball, but you don't want to go crazy to it and for me, I found a happy medium.'
For a more visual example, take a look at the two videos below. Even taking into account the different camera angles, Ackley's stance with the Yankees (video #2) does appear to be different, with his body more squared to the mound, hands cocked, and bat off his shoulder (pause each video at two seconds to compare the stances). As the video plays a second time, notice how much quieter his lower half during the swing appears to be with the Yankees as opposed to with the Mariners a few years ago. Even though both swings resulted in home runs, his stance and swing with the Yankees seems much more compact.
In addition, in Ackley's short stint with the Yankees, it doesn't seem as though he was tempted into trying to take advantage of Yankee Stadium's short right field porch. Encouragingly, he actually pulled the ball less with the Yankees (41%) than he did while with Seattle (44%) in 2015, while seeing the percentage of balls he put in play in the middle of the field rise by nearly five percent. His line drive (+10.6%) and hard-contact rates (+13%) also increased by double-digits. Ackley also typically sees a lot of pitches while at-bat, as his 4.06 pitches-per-plate-appearance would have tied him for 22nd (with Kris Bryant) in 2015 had he had enough at-bats to qualify.
So perhaps his stint with the Yankees in 2015 wasn't a total anomaly. For the record, he is currently off to a nice start this spring, hitting .297/.316/.405. Obviously, spring stats are not the best way to judge a player, especially since Ackley's .324/.375/.503 career line in spring training games (who knew people kept track of career spring stats?) doesn't match up with his regular season production.
However, this is not the typical optimistic "He changed his swing so expect big things this season" story we see in spring training. Ackley has already proven to himself (albeit in a very small sample) that his new stance and swing can be successful against major league pitching. Obviously, his new swing will have to stand the test of a full season to be considered a success, as swing alterations can be very volatile things (see: Derek Jeter, Curtis Granderson), but it does appear that the groundwork is there for him to build upon.