Slugging Percentage
Stat of the Week
by Peter Liubicich
Slugging Percentage
This post was written by Peter Liubicich on March 26, 2012
Posted Under: Stat of the Week

This week we’ll be getting back to basics by covering Slugging Percentage (SLG).  I mentioned Slugging Percentage in my article about Isolated Power, as ISO is intended to measure a player’s raw power and accounts for doubles, triples, and home runs.  SLG, on the other hand, also takes the number of singles a player hits into account.  SLG is an explanatory statistic, rather than a predictive statistic, as it shows a batter’s overall power throughout a season.

The formula for SLG is:

As you can see from the formula, SLG factors in the amount of bases a player touches for each different hit.  Basically, SLG is the average amount of bases a player is expected to touch per at-bat throughout a season, where if a player hit a single every time they had an at-bat their SLG would be 1.000, and if they hit a home run every at-bat, their SLG would be 4.000 (which would be the highest SLG that a player could attain).  It is also important to keep in mind that SLG uses at-bats, rather than plate appearances.  The difference, as I mentioned in this article on Batting Average, is that plate appearances measure the amount of times a batter steps up to the plate, while at-bats do not take sacrifice hits, walks or hit by pitches into account.

To demonstrate how SLG measures a batter’s power let’s quickly look at two players from 2011, Ichiro Suzuki and Jose Bautista.  I chose these two players because Ichiro has racked up over 2428 hits during his 11 year MLB career (even after recording 1278 hits during 9 years in the Nippon Professional League for the Orix Blue Wave) and in 2004 broke George Sisler’s record for most hits, with 262, in a single MLB season which stood for 84 years, but is predominantly a singles hitter.  Jose Bautista, on the other hand has become one of baseball’s most feared power hitters the past two seasons by belting a total of 97 HRs.

Last season, Ichiro had 184 hits including 154 singles, 22 doubles, 3 triples and 5 home runs in 677 at-bats, while “Joey Bats” had 155 hits including 86 singles, 24 doubles, 2 triples and 43 home runs in 513 at-bats.  In terms of SLG, Bautista blew Ichiro away as Bautista’s SLG was .608 and Ichiro had a SLG of .335, showing SLG’s usefulness in explaining which player provided more power to their team.

The all-time career leader in MLB history in SLG, according to Baseball Almanac, is Babe Ruth who had a career SLG of .690, 56 points greater than the next closest player Ted Williams (.634 career SLG) and 73 points higher than the closest active player, Albert Pujols (.617 career SLG).

SLG is also used in a common statistic called OPS (On-Base Percentage plus Slugging Percentage) which I’ll be covering next week to show how teams are evaluating players by combining the statistic that measures a player’s ability to get on base which over the course of a season helps their team score more runs and another statistic which measures a player’s power and the average amount of bases they touch per at-bat.

One final thought, we are only 9 days away from Opening Day with the renamed Miami Marlins debuting their new ballpark, Marlins Stadium, against the reigning World Series Champion St. Louis Cardinals!