Since Pablo Sandoval was introduced to us in 2008, he's been one of the most interesting players to watch in baseball. For seven years with the Giants, fans watched him swing at pitches over his head and below his ankles, but do so in a way that didn't drive them crazy. He was able to hit almost anything that he wanted, and drive it with authority. Sandoval was one of the few players in the game for which a scouting report was nearly useless. He won three championships with the Giants, and hit .337 during the final two playoff runs, while taking home MVP honors in the World Series in 2012.

He was adored by the fans in San Francisco, and while it initially seemed like a foregone conclusion that he'd re-sign with the team he'd been with since he was just 18 years old, he apparently felt disrespected by what the Giants had offered him during spring training in 2014, and bolted to Boston.

While the deal was viewed by most as a good signing, and that Sandoval could eventually take Ortiz's role as the most beloved figure in Boston once he retired, it hasn't been smooth sailing since he moved to the American League.

Year G PA BB% K% ISO BABIP wOBA wRC+ fWAR 2008 41 154 2.6% 9.1% .145 .356 .362 118 0.9 2009 153 633 8.2% 13.1% .226 .350 .399 146 5.2 2010 152 616 7.6% 13.1% .140 .291 .316 96 1.2 2011 117 466 6.9% 13.5% .237 .320 .383 149 5.3 2012 108 442 8.6% 13.3% .164 .301 .338 118 2.6 2013 141 584 8.0% 13.5% .139 .301 .331 118 2.0 2014 157 638 6.1% 13.3% .136 .300 .323 113 3.1 2015 101 297 5.5% 14.4% .127 .283 .303 88 -1.1

For the first time in Sandoval's career, he's on pace to post a negative fWAR. His walk and strikeout rates aren't terribly unexpected give his career norms, but each has moved in the wrong direction in 2015. Regardless of which statistics are highlighted, the only conclusion that can be reached is that Sandoval is struggling mightily, but that doesn't answer the question of what's causing his regression.

One of the first places to look is his splits, as Sandoval is a switch hitter. While he only has 51 at-bats as a right handed hitter vs a left handed pitcher this season, it's abundantly clear that he's having enormous difficulty from that side of the plate, and he's been getting worse every year since 2012.

vs L as R BB% K% ISO wRC+ wOBA 2012 5.8% 13.1% .110 107 .321 2013 9.0% 15.0% .074 101 .307 2014 5.4% 15.1% .120 61 .247 2015 3.7% 25.9% .020 -46 .111

While switch hitting is an incredible skill to have, it's only worth doing if it doesn't prove detrimental to that particular player; unfortunately for Sandoval, he's become worthless from the right side. If he continues to put up numbers like he has in 2015, it might ultimately be necessary for him to give up on it altogether.

He hasn't done it much, but in 71 plate appearances as a lefty, vs a left handed pitcher, Sandoval has posted an ISO of .044, a wRC+ of 81, and a wOBA of .293, which apart from his power would represent an upgrade over the last two seasons. He's not likely going to give up on switch hitting this season or even the next, but if this trend continues, it's something that he and the Red Sox might have to have a conversation about.

As a left-handed hitter, Sandoval has been closer to the offensive player that Boston was expecting, as he's posted an ISO of .169, a wRC+ of 115, and a wOBA of .341. He's even managed to cut down on his strikeout rate by 11.2 percent.

vs R as L BB% K% ISO wRC+ wOBA 2012 9.8% 13.4% .190 123 .345 2013 7.7% 12.9% .164 125 .341 2014 6.5% 12.5% .144 137 .359 2015 6.3% 11.1% .169 115 .341

He's clearly been an above average hitter as a lefty in 2015, but there's still a notable drop-off in production. His wRC+ has fallen by 16.05 percent from last season, and is currently his lowest total since 2010; the year in which he was benched for his poor play.

Sandoval's batted ball ratios have also changed, as he's now hitting more ground balls, and fewer in the air.

Year LD% GB% FB% Soft% Med% Hard% 2008 25.9% 45.2% 28.9% 12.6% 56.3% 31.1% 2009 18.6% 44.9% 36.5% 13.2% 54.0% 32.8% 2010 17.1% 44.4% 38.5% 18.5% 49.9% 31.6% 2011 19.5% 41.6% 38.9% 22.1% 47.4% 30.5% 2012 20.3% 43.0% 36.6% 15.1% 52.6% 32.3% 2013 21.3% 41.5% 37.3% 18.4% 52.3% 29.3% 2014 20.6% 42.6% 36.7% 19.2% 50.0% 30.8% 2015 20.1% 48.6% 31.3% 20.1% 56.2% 23.6%

His ground ball rate has risen by 14.08 percent, while his fly ball rate has fallen by 14.71 percent. He's also not hitting pitches nearly as hard as he used to, and his exit velocity graph resembles something closer to a roller coaster, rather than someone being paid over $17 million for each of the next four seasons.

While the data provided here undoubtedly helps explain why Sandoval is struggling, an article about him wouldn't be complete without mentioning his weight issues. He and the Red Sox have maintained it's not a problem, but he's reportedly "responded to the club's desire that he drop some pounds." One of the reasons that he chose not to stay with San Francisco was because he felt that if he'd "signed (with the Giants) I knew I would be under a (weight) regimen for five years, and I'm not going to be happy someplace where I'm under that kind of regimen, where I can't be myself".

He might not have liked the fact that upper management imposed weight restrictions on him, and forced him to go through offseason workouts, but it's become clear that he doesn't have enough self-control to take it upon himself. It's impossible to know if Sandoval's struggles in 2015 are directly tied to his ballooning weight, but it's likely a contributing factor. His Off and Def ratings are both on pace to set career worsts, at -9.8 and -13.3, respectively, and he simply isn't producing at acceptable levels.

Sandoval might not like when other people meddle in his personal lifestyle, but it's impossible to look past the fact that his best seasons have come when either the Giants put him through a training program, or when his own teammates challenged him to do better. There's no question that Sandoval has an uncanny ability to hit at an elite level, but for a variety of reasons, he hasn't been able to put together any prolonged success in 2015. The Red Sox are on the hook for roughly $82 million, so they desperately need Sandoval to figure things out.

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Matt Goldman is a Featured Writer with Beyond the Box Score and a Contributing Editor at MLB Daily Dish. You can follow him on Twitter at @TheOriginalBull.