For the past decade or so, baseball has played in what we could call the "information era." It began in earnest with the widespread installation of PITCHf/x pitch-tracking technology in 2008. As fans and writers, we've been able to learn a lot about many areas, from the evolving strike zone to pitch-framing to ideal launch angles.
But, of course, the granular information isn't consumed or analyzed only by those outside the game. Information has also been consumed by the players and teams, so certain effects shouldn't be surprising. Pitchers, for example, are more aware of documented hitter weaknesses. And hitters, in turn, are more aware of their own vulnerabilities.
PITCHf/x has been measuring pitches, and the similar HITf/x has been measuring batted balls. More recently, Statcast has entered the mix as a major data source, bringing more information than ever to the table. The Pirates have pointed to the numbers to try to get their hitters to put more balls in the air. Daniel Murphy has pointed to the numbers to try to get Ryan Zimmerman to put more balls in the air. So much data is now available that potential shortcomings can be more quickly identified and addressed.
I've talked to a number of baseball people, and there's a certain shared feeling that now, more than ever before, players are making sudden changes to their approaches.
Many people know about, say, J.D. Martinez and Josh Donaldson and Justin Turner, who decided to try to hit more fly balls. They were responding to data presented to them. They're not alone. Hitters especially are identifying weaknesses and trying to tweak them away, following a few pre-Statcast years of pitchers arguably having the information advantage. Many hitters are swinging at different pitches. Many are just plain swinging differently. The "information era" is now helping to teach hitters how they can defend against good pitching.
As such, many recent articles have been written about hitters who've consciously changed. In a sense, it has become a new genre of analysis. Analysts are able to go into the greatest-ever level of detail. Naturally, changing habits works better for some players than it does for others. You tend to hear more about the success stories. In this article, we'll highlight five hitters who've changed for the better and five hitters who've fallen off a bit.
Let's start with the positive changes.