Casey has a .213 BABIP against left-handed pitchers this year, despite a 19.1% line drive rate, which is actually better than his 15.9% mark against right-handed pitchers. So it's safe to say he's a clear bounce-back guy against left-handed pitchers next year, and overall. If we expand the sample of his hit rate to his entire career, he's hitting .267 against left-handed pitchers in just 367 at-bats, compared to .272 against right-handed pitchers. His BABIP against left-handed pitchers is 16 points lower, despite a line drive percentage 2.1% higher. He also has a better BB/K rate against left-handed pitchers. Conclusion: Casey is definitely not a textbook lefty-killer, but he appears somewhere between as good and mildly better against left-handed pitching than right-handed, despite his record. Perfect platoon candidates would fall further towards the lefty-killer side of the spectrum because you don't have to pay for the player's production against right-handed pitching that you're not using, but that wouldn't prevent me from platooning Casey, at least partially, if Green or Gamel can provide more production.