The Role Swing Percentages Play in MLB Success

Many batters take criticism for their reluctance to swing. Is this criticism justified?

Mel Gibson ain't got time for your working-the-count non-sense, y'all. And he'll go to great lengths to make this fact known.

"Swing away, Merrill. Swing away," Gibson said at the end of M. Night Shyamalan's alien flick, Signs. While on the surface this seems like advice about how to beat the living bejeezus out of an extraterrestrial, that's not the main motivation. He clearly disagrees with Merrill's approach at the plate and thinks that plate discipline is vastly overrated.

As Merrill proceeds to pummel the pest to a pulp, the idea is being planted in your head that in order to succeed, you must swing and swing often. This may seem absurd, but the idea is grabbing on. In fact, some people who are paid to talk about baseball have taken the concept to an extreme.

Gibson and Reynolds have come to the same conclusion: if you don't swing, we all gonna die. I wanted to see if this was true because, if so, that would be mildly concerning.

What I did was look at the plate discipline numbers for each of the 209 batters last year who recorded 400 or more plate appearances. After observing these numbers, it became apparent that the Colorado Rockies players were all fairly significant outliers, so I went all Merrill on those seven suckas and expelled them from my spreadsheets.

I wanted to see if there were any significant trends within the data that could say whether or not it was smart to just let players swing away. Here were some of the takeaways.

The Swingers

The only reason this sub-heading is here is so that I could imagine Pablo Sandoval in a 1920's-era dress with a feather on his head. Mission accomplished, and I immediately regret the decision.

Sandoval did lead the league in swing percentage last year and by a fairly significant margin. Panda swung at 59.5 percent of all pitches last year; no other batter with at least 400 plate appearances did so more than 58 percent of the time.

Sandoval turned his swingin' ways into a .279/.324/.415 slash and a .323 wOBA. These were all above the league averages of .251/.314/.386 and a .310 wOBA respectively. So, swing away, right?

Below is a chart of the players with the top 10 swing percentages last year along with their major rate stats. Pay special attention to the on-base percentage and slugging percentage categories as those were the two most heavily affected by swing percentage.

Pablo Sandoval0.2790.3240.4150.32359.50%
Marlon Byrd0.2640.3120.4450.33057.90%
Juan Uribe0.3110.3370.4400.34057.70%
Carlos Gomez0.2840.3560.4770.36857.30%
Aramis Ramirez0.2850.3300.4270.33456.80%
Adam Jones0.2810.3110.4690.34056.50%
J.D. Martinez0.3150.3580.5530.39156.20%
Chris Johnson0.2630.2920.3610.28956.20%
Salvador Perez0.2600.2890.4030.30355.80%
Adeiny Hechavarria0.2760.3080.3560.29055.30%

Eight of the 10 batters above had a slugging percentage greater than the league average. This is not a surprise when you are able to look at the data as a whole. There was actually a very, very weakly positive correlation between a player's swing percentage and his slugging percentage at 0.1408. That doesn't mean a lot as it is a very low number, but it hints that there might be a weak relationship between the two.

This means that maybe Mel Gibson wasn't as much as a cook (when it comes to baseball, at least) as I had thought. Maybe he just wanted Merrill to see an up-tick in his slugging percentage. I'd buy that.

If you look at the chart above, you can see that, while eight players had an above-average slugging percentage, there were also five that had below-average on-base percentages, and none of them ranked in the top 35 in the league in the category. So if there's a weak positive relationship between slugging percentage and swing percentage, what about on-base percentage?

The Non-Swingers

It should make sense that people with a lower swing percentage would have a higher on-base percentage. In order to take a walk, you, by definition, must not swing at least four times. So all of this is obvious, but I thought it was important to show that having a low swing percentage does not make a person a worse hitter.

The chart below shows the ten players with the lowest swing percentage in the league last year among those who recorded at least 400 plate appearances. Similar to the previous chart, pay most attention to the on-base percentage and slugging percentage categories.

Matt Carpenter0.2720.3750.3750.33933.10%
Brett Gardner0.2560.3270.4220.33137.00%
Jayson Werth0.2920.3940.4550.37737.30%
Elvis Andrus0.2630.3140.3330.29137.50%
Carlos Santana0.2310.3650.4270.35337.70%
Ike Davis0.2330.3440.3780.32438.30%
Robbie Grossman0.2330.3370.3330.30638.50%
Ben Zobrist0.2720.3540.3950.33338.60%
Mike Trout0.2870.3770.5610.40238.80%
Brian Dozier0.2420.3450.4160.34039.00%

First, Mike Trout is not a human. Woof.

Second, every one of the players on that list had an on-base percentage at or above the league average. This was coupled, however, with four guys who had below-average slugging percentages.

If we go the same route as the slugging percentage, we can look at correlation. There was a -0.3158 correlation between on-base percentage and swing percentage. This means that there was a weak negative correlation between the two categories, but still a stronger tie than there was with slugging percentage. As swing percentage goes down, on-base percentage goes up.

Because slugging percentage and on-base percentage measure two way different things, we can also look at wOBA, which combines the two in a manner more effective than OPS. Of the 25 players with the lowest swing percentages, 20 had an above-average wOBA. Of the top 25 big swingers, that number drops a tiny bit to 17. This should be a further illustration that you don't need to swing the bat to be an effective baseball player.

Let's revisit Trout briefly. If we saw higher slugging percentages with the high volume swingers, then why was Trout able to have the third-highest slugging percentage while swinging the bat at a low rate?

The most likely explanation is that correlation is not causation. The other guys probably didn't have good slugging marks because they swung the bat a lot; they probably swung the bat a lot because they could mash when they did.

If you're a guy like Jose Abreu, you can get away with swinging at a bunch of pitches because you make solid contact. If you're Matt Carpenter, however, you need a different approach.

Carpenter most likely would have had a slugging percentage around .375 even if he had swung the bat more. But his 13.4 percent walk rate elevated his on-base percentage to .375, as well, giving him far more value than he would have had if he went with a high-swing approach.

This ties in well with John Stolnis's article yesterday on Joey Votto. Fans (and his own play-by-play broadcaster, apparently) criticize Votto because he doesn't swing the bat often (40.3 percent his last full season in 2013), but this data should show that he doesn't have to. Taking pitches won't preclude someone from posting super silly numbers. And, if you're 31 like Votto, this incentive should just be increasing.

So we can't entirely dispel Mel Gibson's guide to hitting. Maybe Merrill is just a baller who can't miss. But, considering they said he held the record for most strikeouts, maybe taking a few pitches wouldn't have been a bad thing. Either way, I think we can just all thank our lucky stars that we don't have to take batting advice from either Gibson or Harold Reynolds, both equally uninformed when it comes to swing percentages.