Realized Platoon Rates

A couple of months ago, I wrote an article about platoon options, and astute reader Tacocat pointed out that platoon hitters never actually realize their versus left-handed pitcher or versus right-handed pitcher splits that we frequently cite. Instead, platoon hitters start games with a platoon advantage, and then sometimes managers have to leave them in to face same-handed pitchers out of the bullpen.

Daily players use the same decision-making as actual managers. You can choose to start a platoon player because he is facing an opposite-handed starter, but that creates a chance that he could see a plate appearance versus a same-handed reliever later in the game. If you are relying on a split stat versus left-handed or right-handed pitchers to make that start/sit decision, then your platoon hitters will underperform your expectations on average.

Fortunately, we can do better. I started by trying to answer the simple question of how often hitters who start games with the platoon advantage actually see the platoon advantage in all of their plate appearances in those starts. With play-by-play data, that is pretty easy to answer. Since 2002, left-handed hitters have seen the platoon advantage in 82.9 percent of the plate appearances in starts in which the opposing starter was right-handed. Right-handed hitters have seen the platoon advantage in 50.7 percent of their plate appearances in starts in which the opposing starter was left-handed.

Those percentages provide a potential weighting to apply to hitter versus left-handed and versus right-handed splits, but I think they oversimplify the nature of platooning. Many hitters are good enough that they play pretty much every day, and obviously those hitters will sometimes start games in which the opposing starting pitcher provides them a platoon advantage. We shouldn’t expect those hitters to be removed in late-inning situations when same-handed relievers enter the game, so I suspected those percentages somewhat understated how often true platoon players faced opposite-handed pitchers in their platoon starts.

To solve that problem, I needed to answer a separate question of what constitutes a platoon hitter. To do so, I looked at the percentage of all starts hitters saw versus opposite-handed starting pitchers and attempted to find the logical boundaries between everyday players and platoon players. Here are the left-handed hitters from 2015 sorted from the highest to the lowest percentage of starts with the platoon advantage over the opposing starting pitcher to illustrate.

LHBs w/ Highest Pct. of GS w/ Platoon Adv., Min. 40 GS, 2015

Hitter	GS	Platoon Adv vs Starter
Chris Coghlan	119	100.0%
Kelly Johnson	78	100.0%
Andre Ethier	106	99.1%
David Murphy	92	98.9%
Grady Sizemore	66	98.5%
Ike Davis	61	98.4%
Tyler Collins	50	98.0%
Michael Conforto	48	97.9%
John Jaso	48	97.9%
Scooter Gennett	93	97.8%
Skip Schumaker	41	97.6%
David DeJesus	75	97.3%
Seth Smith	107	97.2%
Conor Gillaspie	69	97.1%
Pedro Alvarez	124	96.8%
Alexi Amarista	87	96.6%
Will Venable	81	96.3%
Jake Lamb	89	95.5%
Dustin Ackley	67	95.5%
Ezequiel Carrera	44	95.5%
Ben Paulsen	79	94.9%
Matt Joyce	74	94.6%
Alex Avila	56	94.6%
Miguel Montero	91	94.5%
Clint Robinson	77	93.5%
Carl Crawford	43	93.0%
Matt Adams	42	92.9%
Alejandro De Aza	81	92.6%
Ryan Howard	118	91.5%
Justin Bour	102	91.2%
Travis Snider	65	90.8%
David Peralta	116	90.5%
Derek Dietrich	71	90.1%
A.J. Pierzynski	105	89.5%
Domonic Brown	47	89.4%
Cody Asche	112	89.3%
Eric Sogard	102	89.2%
Kyle Schwarber	59	88.1%
Adam LaRoche	116	87.9%
Stephen Drew	105	87.6%
Ryan Goins	112	87.5%
Adam Lind	135	87.4%
Anthony Gose	125	87.2%
Yonder Alonso	94	87.2%
Jon Jay	53	86.8%
Sam Fuld	75	86.7%
Curtis Granderson	144	86.1%
Gregory Polanco	137	86.1%
Stephen Vogt	115	86.1%
Lonnie Chisenhall	86	86.0%

It isn’t completely cut and dried, but I see the transition for left-handed hitters happening around 89 percent. Just above that threshold are players like Alejandro De Aza, Ryan Howard, and Travis Snider who each had platoon partners I could (sort of) easily identify—Shane Victorino and Rusney Castillo, Darin Ruf, and Steve Pearce and Nolan Reimold. Meanwhile, just below the threshold are players like Kyle Schwarber and Adam LaRoche who generally played every day when they were healthy and on their rosters.

RHBs w/ Highest Pct. of GS w/ Platoon Adv., Min. 40 GS, 2015

Hitter	GS	Platoon Adv vs Starter
Ryan Raburn	50	100.0%
Franklin Gutierrez	42	78.6%
Shane Victorino	50	70.0%
Jake Smolinski	50	68.0%
Brandon Guyer	79	67.1%
John Ryan Murphy	43	65.1%
Clint Barmes	51	64.7%
Mike Aviles	79	64.6%
Josh Phegley	62	64.5%
A.J. Ellis	55	63.6%
Chris Young	77	61.0%
Tim Beckham	51	60.8%
Scott Van Slyke	53	60.4%
Jonny Gomes	55	58.2%
Nolan Reimold	45	57.8%
Wilin Rosario	54	55.6%
Darin Ruf	62	54.8%
Shane Robinson	48	54.2%
Gordon Beckham	50	54.0%
Jeff Francoeur	71	53.5%
Danny Valencia	85	52.9%
Kiké Hernandez	51	52.9%
Jake Marisnick	101	52.5%
Paulo Orlando	63	52.4%
Chris Carter	112	50.9%
Rajai Davis	73	50.7%
Joey Butler	61	49.2%
Melvin Upton Jr.	47	48.9%
Chris Denorfia	45	48.9%
Hernan Perez	66	48.5%
Steve Pearce	79	46.8%
Alex Guerrero	49	44.9%
George Springer	101	44.6%
Peter Bourjos	41	43.9%
Aaron Hill	73	43.8%
Mike Napoli	115	43.5%
Domingo Santana	44	43.2%
Delino Deshields	110	42.7%
Chris Johnson	61	42.6%
Justin Maxwell	59	42.4%
Mark Canha	108	41.7%
Delmon Young	41	41.5%
Kelby Tomlinson	46	41.3%
Robinson Chirinos	73	41.1%
Mark Trumbo	132	40.9%
Evan Gattis	147	40.8%
Michael Morse	57	40.4%
Elvis Andrus	159	40.3%
Jake Elmore	40	40.0%
Adrian Beltre	143	39.9%

From the right side, I’m seriously impressed the Indians were able to start Ryan Raburn in 50 games without any of them having a right-handed starter. More on point, the right-handed threshold is around 45 percent, below players like Chris Denorfia (platooned with Chris Coghlan and Mike Baxter) and Rajai Davis (platooned with Anthony Gose) and above players like George Springer and Mike Napoli.

Next, I recalculated how often hitters who start games with the platoon advantage actually see the platoon advantage in all of their plate appearances in those starts using only hitters who exceeded those thresholds in 40 or more plate appearances each season. That added filter increased the left-handed platoon advantage to 84.9 percent (up 2.0 percent) and the right-handed platoon advantage to 52.6 percent (up 1.9 percent).

The next step will be to use those platoon percentages to project platoon hitters in their daily matchups, but I’ll leave that for next week because I’m tired and because I want to have a chance to read any feedback you may have for me.