Mains: The designated hitter penalty that went away

From SABR member Rob Mains at Baseball Prospectus on June 27, 2018:

Recently, a friend of mine—a Red Sox fan—sent me this e-mail:

J.D. Martinez is hitting .356 in the 30 games he has played in either left or right field. He’s hitting .282 in the 39 games he’s been the designated hitter.

Being an Official Baseball Analytics Person™, I explained why this isn’t surprising. I told him about the Designated Hitter Penalty, a concept introduced by Tom Tango, Mitchel Lichtman, and Andrew Dolphin in The Book.

Players, on average, hit worse in games in which they’re a DH than when they’re in the lineup at an actual defensive position. That’s what was going on with Martinez. In fact, I mused, with huge pitching staffs eating into benches, creating fewer job openings for full-time DHs, the penalty is probably getting larger. Part-time DHs are likely less adept at the position than the David Ortizes and Edgar Martinezes of yore.

Man, I couldn’t have been more wrong.

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Originally published: June 28, 2018. Last Updated: June 28, 2018.