How Plate Discipline Impacts wRC+

Like many of you, I spend hours on FanGraphs trying to take in as much information as possible. One of the more fascinating statistics to me is the category of plate discipline. This includes how often a batter will swing on a pitch inside or outside of the zone, how often a batter swings and misses, and many other variables that affect a player’s approach at the plate. While these numbers alone are a good indication on how a player acts at bat, I wanted to know how these numbers affected performance. For instance, it would make sense that a higher O-Swing% could lead to less-than-average hitting. The 2015 season had Adam Jones second in O-Swing%, swinging at 47% of pitches outside of the strike zone. Pablo Sandoval led the league in O-Swing% with a 48% rate. Jones recorded a 109 wRC+ while the Kung Fu Panda had a 75 wRC+.

By breaking down these Plate Discipline statistics for the 2015 season, I believe that we can get a good answer on which statistic leads to the best performance. For my methodology, I used the wRC+ and Plate Discipline leaderboard for the 2015 season. After breaking down each statistic, I compiled a top 10 and bottom 10 wRC+. Additionally, I grouped percentages to get the number of batters and average wRC+ for certain percentages.

O-Swing %

O-Swing% = Swings at pitches outside the zone / pitches outside the zone

Top 10 wRC+ Average: 97

Name	O-Swing%	wRC+
Pablo Sandoval	47.80%	75
Adam Jones	46.50%	109
Avisail Garcia	45.20%	83
Marlon Byrd	43.90%	100
Salvador Perez	42.50%	87
Kevin Pillar	40.10%	93
Starling Marte	39.40%	117
Gerardo Parra	39.40%	108
Freddy Galvis	39.20%	76
Nolan Arenado	38.50%	119

 

Bottom 10 wRC+ Average: 132

Name	O-Swing%	wRC+
Brett Gardner	22.90%	105
Ben Zobrist	22.60%	123
Matt Carpenter	22.50%	139
Paul Goldschmidt	22.40%	164
Jose Bautista	22.20%	148
Carlos Santana	21.10%	110
Francisco Cervelli	20.90%	119
Dexter Fowler	20.90%	110
Curtis Granderson	19.90%	132
Joey Votto	19.10%	172

 

Percentage	Count	Average wRC+
40%-48%	6	91
30%-39%	73	106
20%-29%	60	117
< 20%	2	152

O-Swing% gives us a pretty good indication of a player’s overall performance. It’s no surprise that patience and a good eye are part of a skill set that leads to a higher wRC+. For each 10-percent decrease of O-Swing percentage, batters see an increase of over 10 points for their wRC+. The top 10 wRC+ compared to the bottom 10 also tells a compelling story of what O-Swing tells us. In the top 10, we see a couple of above-average hitters like Starling Marte and Nolan Arenado. However, we also see five of the top 10 with a wRC+ under 100 and one hitter (Marlon Byrd) at 100. On the other side of the spectrum, there isn’t a hitter under 100 wRC+ in the bottom 10. The difference in wRC+ between the top and bottom 10 is 35, the biggest difference between all the statistics.

Let’s look at two very different extremes: Joey Votto and Pablo Sandoval. Sandoval had an O-Swing% of 48 percent while Votto had a 19 percent rate, which means that while Sandoval is swinging at almost half of the balls he faces, Votto is taking a little more than 80% of pitches out of the zone. Sandoval faced 1848 pitches (1287 strikes to 561 balls) while Votto faced 3020 pitches (1644 strikes to 1376 balls). Sandoval’s more than double strike-to-ball ratio and Votto leading the league in walks can both be explained by their O-Swing percentage.

Z-Swing %

Z-Swing%  = Swings at pitches inside the zone / pitches inside the zone

Top 10 wRC+ Average: 111

Name	Z-Swing%	wRC+
Marlon Byrd	83.20%	100
Brandon Belt	80.90%	135
Adam Jones	80.60%	109
Avisail Garcia	78.90%	83
Billy Burns	78.80%	102
Carlos Gonzalez	78.10%	114
Ryan Howard	77.80%	92
Starling Marte	77.50%	117
Kris Bryant	76.20%	136
Brandon Crawford	76.10%	117

Bottom 10 wRC+ Average: 115

Name	Z-Swing%	wRC+
Carlos Santana	57.90%	110
Logan Forsythe	57.70%	126
Joe Mauer	57.50%	94
Brock Holt	57.40%	98
Brett Gardner	55.80%	105
Brian McCann	55.80%	105
Mookie Betts	55.70%	119
Mike Trout	55.60%	172
Ben Zobrist	55.40%	123
Martin Prado	53.20%	100

 

Percentage	Count	Average wRC+
80%-83%	3	115
70%-79%	51	111
60%-69%	75	110
50%-59%	12	114

The first thing that I noticed when looking at the Z-Swing charts is the duplication of names from the O-Swing charts. Adam Jones, Avisail Garcia, Marlon Byrd, and Starling Marte showed up on both the O and Z Swing percentage top-10 while Ben Zobrist, Carlos Santana, and Brett Gardner appeared on both bottom-10 lists. This is a very mixed bag of players for both the top and bottom. Both have a 100 wRC+ hitter, the epitome of average. Both have seven hitters batting above 100 wRC+ meaning that both lists also have two hitters batting below 100. The top and bottom 10 averages are almost even. The one outlier that separates them is Mike Trout in the bottom 10 with a 172 wRC+. Seeing the same name on multiple lists can tell us a lot about a player. Someone like Marlon Byrd will swing at most of the pitches you send his way while Ben Zobrist will take a pitch outside of the zone about 77% of the time but will also take a strike 45% of the time as well.

O-Contact %

O-Contact% = Number of pitches on which contact was made on pitches outside the zone / Swings on pitches outside the zone

Top 10 wRC+ Average: 104

Name	O-Contact%	wRC+
Nick Markakis	86.10%	107
Michael Brantley	84.60%	135
Daniel Murphy	83.50%	110
Ender Inciarte	82.30%	100
Melky Cabrera	82.10%	91
Wilmer Flores	82.00%	95
Jose Altuve	81.70%	120
Ben Zobrist	80.90%	123
Angel Pagan	80.80%	81
Yadier Molina	80.20%	80

 

Bottom 10 wRC+ Average: 104

Name	O-Contact%	wRC+
Anthony Gose	55.00%	90
Avisail Garcia	55.00%	83
Nick Castellanos	53.20%	94
Ryan Howard	52.80%	92
Michael Taylor	52.10%	69
Justin Upton	51.50%	120
Addison Russell	51.10%	90
Chris Davis	50.90%	147
Kris Bryant	49.20%	136
Joc Pederson	49.00%	115

 

Percentage	Count	Average wRC+
80%-86%	10	104
70%-79%	46	103
60%-69%	60	118
50%-59%	23	105
< 50%	2	126

Similar to Z-Swing%, O-Contact doesn’t show much disparity between the top and bottom 10. In fact, they’re identical at 104 wRC+. A higher O-Contact gives a batter more balls in play, but doesn’t always lead to success. My initial thought was that swinging at a pitch way out of the zone can lead to weak contact, and usually an out. The fact the top and bottom are identical shows that this isn’t always the case.  It also makes sense why the middle of the pack (60%-69%) has the greatest wRC+ (besides the small sample size of < 50%). These batters are still able to make contact with pitches outside of the zone more than half of the time, but also miss the pitch enough of the time where they don’t make bad contact.

Z-Contact %

Z-Contact%  = Number of pitches on which contact was made on pitches inside the zone / Swings on pitches inside the zone

Top 10 wRC+ Average: 110

Name	Z-Contact%	wRC+
Daniel Murphy	97.50%	110
Ben Revere	96.70%	98
Michael Brantley	96.30%	135
Yangervis Solarte	95.50%	109
Martin Prado	95.40%	100
A.J. Pollock	94.60%	132
Jose Altuve	94.60%	120
Ian Kinsler	94.50%	111
Erick Aybar	94.30%	80
Ender Inciarte	94.20%	100

 

Bottom 10 wRC+ Average: 125

Name	Z-Contact%	wRC+
Mark Trumbo	80.90%	108
Brandon Belt	80.70%	135
J.D. Martinez	80.60%	137
Nelson Cruz	79.30%	158
Justin Upton	78.00%	120
Michael Taylor	77.40%	69
Joc Pederson	77.00%	115
Chris Davis	76.50%	147
Alex Rodriguez	76.50%	129
Kris Bryant	75.80%	136

 

Percentage	Count	Average wRC+
90%-98%	55	106
80%-89%	79	113
70%-79%	7	125

Z-Contact was the most surprising statistic in terms on its effect on wRC+, until you look at the names in the bottom 10. One would expect that hitters that hit more pitches in the zone would be the better performers. However, the bottom 10 is filled with power hitters, leading to the main difference in wRC+. Davis and Cruz were number one and two in terms of home-run leaders in 2015. In fact, besides Michael Taylor, the bottom 10 is all in the top 50 for home runs in the MLB. The list makes sense as players like Chris Davis are trying to “Crush” the ball out of the park and swing harder than someone in the top 10 like Martin Prado.

SwStrike %

SwStr% = Swings and misses / Total pitches

Top 10 wRC+ Average: 110

Name	SwStr%	wRC+
Avisail Garcia	17.30%	83
Marlon Byrd	17.20%	100
Ryan Howard	16.60%	92
Kris Bryant	16.50%	136
Michael Taylor	16.00%	69
Chris Davis	15.60%	147
Carlos Gonzalez	15.20%	114
J.D. Martinez	14.90%	137
Mark Trumbo	14.60%	108
Joc Pederson	14.00%	115

 

Bottom 10 wRC+ Average: 105

Name	SwStr%	wRC+
Ian Kinsler	5.20%	111
Ender Inciarte	4.90%	100
Andrelton Simmons	4.90%	82
Angel Pagan	4.40%	81
Martin Prado	4.30%	100
Ben Zobrist	4.20%	123
Nick Markakis	4.10%	107
Ben Revere	4.10%	98
Daniel Murphy	3.90%	110
Michael Brantley	3.10%	135

 

Percentage	Count	Average wRC+
15%-18%	7	106
12%-14.9%	20	107
9%-11.9%	36	117
6%-8.9%	50	114
3%-5.9%	17	106

Not surprisingly, the top 10 for SwStrike looks a combination of both the O-Contact and Z-Contact bottom 10. Obviously if your contact is low, you’re going to have more swings and misses. The main factor that stood out to me looking at the top and bottom 10 is the deviation of wRC+. The top 10 is all over the place, having players like Kris Bryant with a 136 wRC+, Michael Taylor with 69, and every level of player in between. The bottom 10 has less variation, providing a more consistent group of hitters.

Totals

Category	Top 10	Bottom 10	Difference (Bottom to Top)
O-Swing%	97	132	35
Z-Swing%	111	115	4
O-Contact%	104	104	0
Z-Contact%	110	125	15
SwStr%	110	105	-5

 

As evidenced by the chart, the main statistic in regards to plate discipline to show a great change in performance that compares the bottom to the top level is O-Swing percentage. Z-Contact seems to also be relevant when evaluating and predicting a player’s performance.