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In the first season of the Statcast era, batted-ball exit velocity has been an exciting statistic for baseball fans to get their hands on, but before we have a full season of data under our belts it’s the Wild West, as it’s difficult to draw any conclusions. Still, here’s an attempt to examine how exit velocity has affected performance at the plate with some of the numbers we have.

Below are the five greatest increases and the five greatest decreases in batted-ball velocity in June compared to May (with at least 30 balls in each month), followed by their BABIP, ISO, Soft, Hard, and Medium percentages in each month, and charts plotting the exit velocity of all their batted balls in each month. This is, by no means, a scientific study, as the small sample and arbitrary markers of calendar months will show you. It’s still interesting to look at how big swings in average exit velocity have impacted different aspects of offensive performance. I chose BABIP and ISO because they’re the best way to get a back-of-the-envelope estimate of what a hitter does when he puts the ball in play. The quality-of-contact percentages break down how a hitter increased or decreased his velocity. They show, for example, if a player increased his hard-hit balls at the expense of his medium-hit balls or if at the expense of his soft-hit balls.

I didn’t include trajectory data like line drive percentage because it seems that the two don’t correlate. Because they are unrelated, it would be interesting to see if batted-ball trajectory or average exit velocity has a greater effect on hitter success. We’ll check back on these players to see if they sustained their velocities in July.

Yoenis Cespedes
Batted Balls in May: 69
Batted Balls in June: 58

Exit Velocity

BABIP

ISO

Soft%

Medium%

Hard%

May

90.10

.333

.164

11.9%

56.0%

32.1%

June

97.47

.365

.168

6.5%

57.1%

36.4%

Difference

+7.37

+.032

+.004

-5.4%

+1.1%

+4.3%

Cespedes increased his average exit velocity more than anyone else, and he also had the highest average exit velocity of anyone that month. His BABIP shot up from pretty high to really high, but his ISO didn’t budge. His soft, medium, and hard percentages were also unchanged compared to some of the other players on this list.

J.J. Hardy
Batted Balls in May: 45
Batted Balls in June: 55

Exit Velocity

BABIP

ISO

Soft%

Medium%

Hard%

May

84.89

.215

.083

25.0%

55.9%

19.1%

June

91.64

.366

.091

15.3%

52.8%

31.9%

Difference

+6.75

+.151

+.008

-9.7%

-3.1%

+12.8%

Hardy’s BABIP varied widely. The balance between random fluctuation and the 7 mph increase in exit velocity is impossible to discern. Like Cespedes, while Hardy’s BABIP increased a significant amount, his ISO remained relatively constant.

Mike Aviles
Batted Balls in May: 32
Batted Balls in June: 41

Exit Velocity

BABIP

ISO

Soft%

Medium%

Hard%

May

83.41

.333

.106

19.1%

57.1%

23.8%

June

89.37

.250

.016

14.3%

55.4%

30.4%

Difference

+5.96

-.083

-.090

-4.8%

-1.7%

+6.6%

Aviles’ performance seems inexplicable. His average exit velocity went up by nearly 6 mph, yet his BABIP and ISO sunk. Aviles batted .230/.266/.246 in June as his line drive rate dropped from 33 percent in May to 9 in June. He hit groundballs well over half the time. Aviles was able to hit the ball harder in June—he just hit it in the wrong places.

Justin Maxwell
Batted Balls in May: 31
Batted Balls in June: 31

Exit Velocity

BABIP

ISO

Soft%

Medium%

Hard%

May

85.71

.304

.032

31.9%

44.7%

23.4%

June

90.71

.162

.167

17.5%

57.5%

25.0%

Difference

+5.00

-.142

+.132

-14.4%

+12.8%

+1.6%

Maxwell’s BABIP plummeted from .304, just points away from his career average of .296, to an abnormal .162. This can’t be explained away by batted-ball trajectory like Aviles’ quandary can: While Maxwell’s line drive percentage decreased, it did so only slightly. Maxwell probably had a string of bad luck, which explains part of the decline.

Maxwell’s ISO boost was partially fueled by the fact that he tallied three home runs and one double out of nine hits he collected in June. It’s a (say it with me) small sample, and the average exit velocity on those four extra-base hits was 84 mph. An interesting aspect of Maxwell’s profile is that his medium percentage increased so much while his hard percentage barely ticked up at all. This is apparent as well when looking at the graph. The peaks aren’t much higher, but the troughs are far less low.

Mark Teixeira
Batted Balls in May: 61
Batted Balls in June: 54

Exit Velocity

BABIP

ISO

Soft%

Medium%

Hard%

May

85.71

.239

.247

20.8%

49.4%

29.9%

June

90.48

.270

.247

13.2%

54.4%

32.4%

Difference

+4.77

+.031

0

-7.6%

+5.0%

+2.5%

Teixeira was able to push his BABIP up in June, but his ISO stayed exactly the same. He hit more line drives and fewer groundballs during the month, partially explaining how he was able to lift his notoriously low BABIP during the month. The majority of Teixeira’s increase, like Maxwell’s, came in the form of soft contact transforming into medium contact. It’s possible that increases in the exit velocity of individual batted balls don’t matter until they reach a certain level.

Steven Souza
Batted Balls in May: 32
Batted Balls in June: 44

Exit Velocity

BABIP

ISO

Soft%

Medium%

Hard%

May

93.97

.350

.274

25.5%

25.5%

48.9%

June

86.00

.206

.152

19.4%

59.7%

20.9%

Difference

-7.97

-.144

-.122

-6.1%

+34.2%

-28.0%

It was a rough month all around for Souza, but an interesting one. He possesses the single greatest change in average exit velocity from May to June, and he did it in an odd way. He hit fewer balls softly, but he hit far fewer balls hard, as almost 60 percent were clustered in the medium category in June. Souza struck out a ton in May—just a shade under 40 percent—which is why he had an unremarkable .238 batting average and .333 OBP. When he did hit the ball, however, he was dynamite, as nearly 50 percent of his balls were hard-hit. His 94 mph average exit velocity was ninth in baseball among players with at least 30 batted balls in the month.

It appears that May was more an aberration for Souza than June. Although it’s difficult to tell what an aberration is when we have just three and a half months of data, Souza’s average exit velocity in April was between that of May and June: 89 mph. He has too much fluctuation and we have too little data to draw any conclusions from this. We do know is that Souza has had a roller coaster ride of a season, and that has been reflected in his batted ball profile.

Andre Ethier
Batted Balls in May: 53
Batted Balls in June: 57

Exit Velocity

BABIP

ISO

Soft%

Medium%

Hard%

May

90.53

.329

.172

15.1%

49.3%

35.6%

June

82.97

.222

.202

19.4%

53.7%

26.9%

Difference

-7.56

-.107

+.030

+4.3%

+4.4%

-8.7%

Ethier’s decline in BABIP is likely due in part to random fluctuation, in part to his drop in line drive percentage, and in part to his decrease in exit velocity. His increased ISO probably came about as a result of an increased HR/FB ratio.

Brian Dozier
Batted Balls in May: 55
Batted Balls in June: 60

Exit Velocity

BABIP

ISO

Soft%

Medium%

Hard%

May

92.27

.316

.343

15.7%

43.4%

41.0%

June

85.20

.304

.269

23.3%

43.0%

33.7%

Difference

-7.07

-.012

-.074

+7.6%

-0.4%

-7.3%

Dozier’s decrease in exit velocity is garden-variety, with most of his missing hard-hit balls being replaced directly by softly hit ones, with little change in medium-hit balls. Dozier was able to keep his BABIP relatively high in June, which is strange, given the decrease in exit velocity accompanied by the decrease in line drive percentage.

Mike Moustakas
Batted Balls in May: 39
Batted Balls in June: 55

Exit Velocity

BABIP

ISO

Soft%

Medium%

Hard%

May

91.18

.301

.153

14.7%

61.3%

24.0%

June

85.02

.321

.113

20.9%

47.7%

31.4%

Difference

-6.16

+.020

-.040

+6.2%

-13.6%

+7.4%

Moustakas had the opposite month from Souza: Instead of his balls migrating toward the medium category, they migrated away from it. Moustakas hit more balls softly in June, as the six-percentage-point increase from May will tell you. Moustakas also hit his softly hit balls more softly in June, as the deeper troughs on his graph for June show. This dragged down his overall average exit velocity.

However, if one starts hitting his softly hit balls even softer, it likely won’t matter. It’s not much harder for a major league infielder to field a 70 mph grounder than it is a 60 mph grounder. There’s probably a greater disparity, instead, in the difficulty of fielding a 90 mph grounder versus 100 mph. Thus, while the magnitude of Moustakas’s softly hit balls dragged down his exit velocity for the month, his performance was assisted by the increased frequency of his hard-hit balls.

Matt Joyce
Batted Balls in May: 43
Batted Balls in June: 38

Exit Velocity

BABIP

ISO

Soft%

Medium%

Hard%

May

88.33

.245

.233

15.8%

52.6%

31.6%

June

82.21

.283

.283

19.2%

61.7%

19.2%

Difference

-6.12

+.038

-.141

+3.4%

+9.1%

-18.4%

Joyce’s BABIP came up from an abnormally low level and moved to within a point of his .282 career average despite a 6 mph decrease in exit velocity. Besides small sample size, an explanation for this is a seven-percentage-point increase in line drives in June.

Thanks to Daren Willman and BaseballSavant.com for help with accumulating exit velocity data.

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LlarryA
7/15
The varying "correlation" between the exit velocity and BABIP with the categories of contact makes me think that the height of the contact (GB/LD/FB) matters as much or more than the solidity of the contact. Might want to try and break it down with both together to see if there's a more consistent pattern of results.

As to Tex's ISO, I think you also have to consider there may be a ceiling he's running into (a couple of the other guys might have lower personal ceilings and be running into them). A .247 ISO is pretty impressive already, and no matter how much harder he hits the ball, it's just not going to go much higher. If *every* ball could be a Hard hit FB or LD, maybe...