Through July 2015, Daniel Murphy had a perfectly fine career going. He'd hit 54 homers over 3,407 plate appearances with a .748 OPS -- solid for an infielder with an iffy glove -- and earned a spot on the 2014 NL All-Star team.
At some point that season, however, Murphy turned into a different player. Since then, he has clubbed 33 homers in 794 regular-season plate appearances, posted an OPS of .950, added another All-Star appearance and finished second in the 2016 NL MVP voting. None of this even addresses the seven homers and 1.092 OPS Murphy recorded over the past two postseasons.
For all the brain capacity and computing power that has gone into developing baseball projection systems, nothing could have predicted Murphy's dramatic rise. You can't foresee something that simply should not happen, and baseball actuarial tables simply cannot account for a player past age 30 tacking 200 points of OPS to his established baseline.
But it didn't just happen, of course.
Murphy made it happen by changing his approach at the plate, and rarely have mid-career adjustments paid off so handsomely. There's a lesson here: A player's skill level does not have to remain static. It can change through work and reasoned experimentation. The career actuarial table is not set in stone, not for the hard-working and the self-aware.
Murphy's evolution can be described by metrics that didn't even exist a few years ago. Thanks to tracking data generated by MLB's StatCast cameras and shared via www.baseballsavant.mlb.com, we now know this: In Murphy's near MVP breakout last season, he actually didn't generate much more pop on contact than he did in 2015, and he ranked around the 81st percentile in both seasons.
However, the angles with which Murphy launched the ball changed drastically, moving from about the 62nd percentile to the 86th (for a nitty gritty on the sweet spots in StatCast data, check this out). Because Murphy's exit velocity was already superb, ranking in the top fifth in all of baseball, the launch angle adjustment generated amazing results.