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Aaron Hill: Where Are You Going, Where Have You Been?

The key to the slugging second baseman's future lies in his past -- and some potentially-ephemeral ground-ball magic.

Mark J. Rebilas-US PRESSWIRE

On August 23, 2011, before the waiver portion of the trade deadline had passed, Aaron Hill was dealt from the Blue Jays to the Diamondbacks in exchange for Kelly Johnson. It was something of a challenge trade, with two disappointing second basemen who had been productive in the past swapped for each other, in the hopes of reigniting whatever it was that made them appealing in the first place. While Johnson rebounded somewhat with the Jays, Hill made a full return to form, and now, after a strong 2012, is the owner of a three-year, $35 million extension that kicks in after this season.

How did Hill get from change-of-scenery candidate to a guarantee of over $40 million over the next four seasons, all in a matter of a year and change? That he's hit .304/.364/.517 in189 games with the Diamondbacks is the obvious answer, but there's more to Hill's performance than a simple rebound back to where he was expected to be following his breakout 2009. In fact, it's a little tough to declare that there was any real rebound here at all, at least not one that can guarantee the dark days of 2010 and 2011 are behind him forever.

To understand where he is, you need to know where Hill came from. He was a well-regarded prospect and young player, one who broke out in 2009 with a .286/.330/.499 line that included 36 homers and 37 doubles. The homers made his season appear a bit better than it was, but his OPS+ was still plenty good at 114. Until 2012, that was his career-best season. In 2010, Hill saw his line crater to .205/.271/.394. His power remained to a degree; despite the severe dip in average, his isolated power only fell from .213 to .189. However, not all of the loss of batting average was luck-based. Yes, his batting average on balls in play fell from a normal .288 to just .196, but a lot of that was Hill's own doing.

Fly ball and line drive rates aren't entirely reliable, as plenty of observer bias is inherent in determining which is which, but it's hard to ignore what the two say about Hill's 2010. His liner rate dropped from just under 20 percent to nearly 11 percent, and that, combined with a slight dip in grounders, all went into his fly ball rate. Fly balls have the lowest BABIP of the three primary batted-ball types, so when Hill started to hit a fly ball nearly six out of every 10 times he put the ball in play, his BABIP plummeted.

Again, some might have been luck, but Hill's approach and swing had a lot to do with the change. Hill was seemingly swinging for the fences every time out, the result of both his success in 2009 as well as the Jays' grip-it-and-rip-it approach of the last few years. While he hit 26 homers, they also accounted for just under a quarter of his total hits, his fly balls yielding a .092 BABIP, or one about 50 points below the league-average BABIP on fly balls. In 2009, his BABIP was just .096 on fly balls, but he went yard an additional nine times while also producing higher BABIP on other batted-ball types. Between the extra homers and his success elsewhere, it was tough to argue his approach was an issue until 2010 showed its downside.

Hill increased his BABIP on fly balls in 2011, bumped his liners back up to his career norms, and managed a grounder BABIP that at least resembled the league-average. The problem was that his power had vanished, at least while with Toronto: Hill was hitting .225/.270/.313 at the time of the trade, or, somehow about 20 percent worse than he did during the to-that-point least productive year of his career. This was akin to his pre-breakout 2008, a .263/.324/.361 affair truncated by a concussion -- his power had vanished, but unlike in 2008, the hits weren't falling in. It was safe to say Hill's approach yielded inconsistent results.

Enter the Diamondbacks. Hill played his first game with Arizona on August 24 of 2011, and in the 142 plate appearances he collected before year's end, he compiled a .315/.386/.492 line that looked like nothing he had accomplished before. He hit just two homers in that stretch, but popped 16 extra-base hits overall while pushing his strikeout:walk ratio as close to even as it's ever been in his big-league career. His 80 plate appearances at Chase Field helped, but Hill still slugged .466 on the road in the limited sample.

The 2012 season was more of the same: Hill extrapolated his impressive 2011 D'backs work into 156 games of greatness, posting a new career-high OPS+ of 131 courtesy of his .302/.366/.502 line, one that was built both with work at home (.321/.365/.564) and on the road (.283./.355/.478). While those might look widely disparate results, players are typically better at home: Hill's Chase line was about 48 percent better than your average positional player at home, and 35 percent better than average on the road.

What was the difference, though? He continued to hit liners around his career rate, rather than 2010's aberrant percentage, but he was unable to match the league average on that number's BABIP (.670 against the league's .709). He did manage to keep his fly ball BABIP out of the gutter, and hit 24 homers and 44 extra-base hits overall via that route, according to Baseball Reference. However, the item that stands out is on grounders: he hit them at about the same rate as usual, but his BABIP spiked from .227 to .300, far outpacing the league-average of .238.

What will this mean for Hill? It's likely he'll be as unpredictable as ever, given how much his game relies on his ability to put as many fly balls where they ain't as he can in a year. He's never been much of a line drive hitter, and his average suffers for it unless he hits fly balls in such a way that he gets away with the approach, as he did in 2012. The real key going forward, though, is the grounders: he'll need to maintain a near-average rate going forward, as he did in 2011, or else there will be trouble.

There's a very good chance Hill will never have another season as good as 2012. He'll be a 31-year-old second baseman, and they don't always age well, but he also has to grapple with the fact that part of his return to form was actually luck -- Hill is quick on his feet, but he's not .300 BABIP on grounders quick. His contract isn't for that much money, though, not in this land of endless television money and ever-rising salaries. In short, even should he fall short, the deal shouldn't cripple the Diamondbacks by any means, even if disappointment were to start now: he just might not be quite the impact player he was in 2012 again over the next four years. Hill will keep swinging for the fences all the same, though, and when it does work, it'll be a thing of beauty.

Marc Normandin is one of SBN's Designated Columnists and one of the managers of Over the Monster. Follow him at @Marc_Normandin and the Designated Columnists at @SBNMLBDCers.