Sunday Morning Sabermetrics: The Slash Line for Hitters

Image Credit: Fangraphs

Last week on Sunday Morning Sabermetrics, we covered Wins Above Replacement (WAR), the cumulative statistic. WAR is a difficult stat to break down fully, but it can best be described as a combination of rate stats for hitters and pitchers multiplied by time (plate appearances or innings pitched). For hitters, the most fundamental of the rate stats is the Slash Line, a five-part stat consisting of Batting Average (BA), On Base Percentage (OBP), Slugging Percentage (SLG), On Base Plus Slugging (OPS), and Adjusted On Base Plus Slugging (OPS+).


BA = Hits/At Bats


OBP = (Hits + Walks + Hit By Pitches)/(At Bats + Walks + Hit By Pitches + Sacrifice Flies)


SLG = Total Bases/At Bats




OPS+ = 100*((OBP/League Average OBP) + (SLG/League Average SLG) – 1) + Ballpark Adjustment


Batting Average is the statistic almost all baseball fans are at least somewhat familiar with, developed by Henry Chadwick in 1859. Chadwick also developed the Earned Run Average for pitchers, another basic stat that we’ll cover in a few weeks. It is calculated as Hits/At Bats, a one variable over another statistic.

Batting Average has several deficiencies. It does not take into account a hitter’s ability to draw a base on balls (a walk), or hit for power. In the early days of baseball, a hitter drawing a walk was not seen as an accomplishment. It was seen as incompetence on behalf of the pitcher. In fact, a walk used to be scored an error on the pitcher that allowed the batter to reach base. Eventually, baseball coaches and scouts realized that it is possible for a hitter who draws a lot of walks to do so because of talent, plate discipline, and the ability to work the count and lay off close pitches. But Batting Average, the old school stat, has stuck around and is still the go-to among the casual fan today.

The classical baseball thought is that a hitter is good if he can maintain at least a .300 batting average, because that is a relatively high number of hits per at bat compared to other players. But it is possible for hitters with lower batting averages to actually be better hitters in the aggregate than their peers who post higher batting averages. OBP, SLG, OPS, and OPS+ help uncover this.

By now, many baseball fans and almost all writers who vote on annual awards and the Hall of Fame are aware that Batting Average is inferior to OBP, SLG, OPS, and OPS+. Batting Average used to be the be-all, end-all stat. In fact, teams used to be ranked offensively based on team Batting Average rather than the one number that matters, runs. That is not the case anymore. We know the Blue Jays had the best offense in baseball last year even though they did not have the highest team batting average. The Jays scored 891 runs in 2015, an incredible 127 more than the next highest team run total.

Washington Nationals outfielder Bryce Harper was the unanimous NL MVP in 2015 despite not leading in batting average. Harper led all of baseball in OBP, SLG, OPS, and OPS+ last year, more impressive and more valuable than winning a batting title, last year accomplished by currently suspended Marlins second baseman Dee Gordon.


On Base Percentage is one of the best offensive statistics available, because the basic rules of the game of baseball tell us that until there are three outs, anything is possible. Once there are three outs, nothing is possible. That being said, the best thing a hitter can do is not cost his team an out. Whether he does that by getting a base hit or drawing a walk should matter very little in the eyes of coaches, scouts, and front offices. Before three outs, a team could theoretically score one hundred runs in an inning. However, probability tells us that the likelihood of a one hundred run inning is negligible and that it is acceptable to ignore it, but since baseball is not played against a clock, the defensive team has to earn three outs before the inning is complete.

OBP also disdains the Sacrifice Fly, which is not really an accomplishment by the hitter. A hitter is credited with an RBI because there was a runner on third base with less than two outs. Normally, a routine fly ball does not earn the hitter praise from his teammates and coaches. But with a runner on third base with less than two outs, that hitter becomes an heir of fortunate circumstances, even a mere fly ball gets the run in and high fives from the team. It is really the runner who stood on third who deserves the credit for getting on base and putting his team in a position to have the next batter be able to knock in the run without that batter getting on base himself.


Slugging Percentage is essentially Batting Average that rewards hitters for hitting for power, getting a hit and one worth multiple bases at that. It is another one variable over another statistic, Total Bases over At Bats. Total Bases is computed as follows: Hits + Doubles + 2*Triples + 3*Home Runs, or, 1*Singles + 2*Doubles + 3*Triples + 4*Home Runs.

OPS is OBP + SLG. OPS has become popular in recent years since it is like an improved, more telling version of the Batting Average, taking into account walks and power hitting. However, OPS has one major shortcoming. It treats OBP and SLG the same; they are weighted equally in calculating OPS. That is not how it should be. OBP is more valuable than SLG, in fact, an extra point of OBP is roughly three times as valuable as an extra point of SLG. To correct this, Tom Tango, author of The Book: Playing the Percentages in Baseball, developed a statistic known as “Weighted On-Base Average”, which we will cover next Sunday.

Adjusted OPS is essentially the unadjusted OPS described above but a relative measure compared to the rest of the league, while accounting for the player’s home ballpark. An OPS+ of 100 always represents the league average. An OPS+ above 100 is better than average, while an OPS+ below 100 is worse than average. In 1999, one of the highest run scoring seasons ever, that league average was .782. In 2014, an offensive drought, average OPS was down to .700. If all I know about a player is that he had an unadjusted OPS of .750 and I can’t remember the league average OPS from that year, I have no idea whether or not he was better or worse than league average. OPS+ is independent of the season, meaning you can look at the number and know whether the player was relatively better or worse, regardless of the kind of offensive season the league as a whole experienced.

OPS+ also includes a ballpark adjustment. An unadjusted OPS of .900 in the thin air of Coors Field is not as impressive as an unadjusted OPS of .900 in the pitcher-friendly dimensions of Petco Park, the host of the 2016 MLB All-Star Game. Hitters home to parks that tend to benefit hitters, such as Coors Field, Camden Yards, Fenway Park, and Globe Life Park, receive penalties when calculating OPS+. By contrast, hitters home to parks that tend to favor pitchers, such as Petco Park, Safeco Field, AT&T Park, and Angels Stadium, receive bonuses.

Perhaps the best way to illustrate the OPS+ ballpark adjustments is comparing the Slash Lines of two players in 2016: Mike Trout of the Angels and Nolan Arenado of the Rockies. Trout has an unadjusted OPS of .936; Arenado’s is higher at .952. This means Arenado is the better hitter, right? Wrong. First of all, Trout has a much higher OBP (.409) than Arenado (.366). Second of all, Angels Stadium is the most pitcher-friendly park in baseball, while Coors Field is the most hitter-friendly – by far. Trout’s adjusted OPS is 159, Arenado’s is much lower at 133 despite the higher unadjusted OPS. This discrepancy is due to the ballpark adjustment (Imagine what a monster Trout would be if he played for the Rockies.).

In addition, it is important to distinguish players across eras. This can be done with Hall of Fame shortstop Honus Wagner, who played in the Dead Ball Era and had a career OPS and OPS+ of .858 and 151, respectively, and near-unanimous Hall of Famer Ken Griffey Jr., who played in the Steroid Era and had a career OPS and OPS+ of .907 and 136, respectively. Although Griffey Jr. did not use steroids, he benefited from having teammates who cheated, such as Alex Rodriguez. Cheaters as Rodriguez protect those around them in the batting order, and make the pitcher’s job harder, indirectly benefiting even their clean teammates as Griffey Jr. Wagner’s .858 OPS, in an era when offense was parched, is more impressive than Griffey’s .907 in an era when offense was at a high, hence the higher OPS+ for Wagner.


I noted last week how we would talk about Boston Red Sox DH David Ortiz during the Slash Line article. OPS+ is especially interesting when you look at the numbers of a player like Big Papi, who has been a Major Leaguer for 20 years and experienced both peaks and valleys in terms of league-wide offense. Before 2016, Ortiz had the three greatest years of his outstanding career in 2005, 2006, and 2007, when he posted OPS of 1.001, 1.049, and 1.066, and OPS+ of 158, 161, and 171. An OPS over 1.000 is excellent, as is an OPS+ over 150, time-and-a-half as good as league average.

Now it is 2016. David Ortiz is 40 years of age and playing his final season, and leading the vicious Red Sox offense that is on pace to score 938 runs, 47 more than even the mighty Blue Jays offense could muster in 2015. Offense around the MLB has risen slightly after bottoming in 2014 but still is nowhere near the level it was in Ortiz’s incredible three-year run in the mid-2000s. David leads the AL in OBP with a .424. Anything over .400 in an era as this, with defensive shifts, faster fastballs, and growing strike zones (whether a conscious effort by the umpires or not), is spectacular. Ortiz leads all of baseball in SLG with a .723. To put that number in perspective, Jose Abreu led the majors with a mere .581 SLG just two years ago. Ortiz’s unadjusted OPS is 1.147, the highest in baseball and the highest of his career. Even more incredible is the OPS+ Ortiz is maintaining in 2016. Currently sitting at 197, David Ortiz, age 40, is the best in baseball and almost twice as good as league average, and actually did reach a 200 OPS+ at one point last week. Dodgers lefty Clayton Kershaw, the modern Koufax, had a 197 ERA+ (basically a pitching OPS+ that we’ll talk about in a few weeks) in 2014, when he won the MVP as a pitcher.


OPS+ puts things in perspective! That’s what we need in baseball. As a fan, don’t just look at a guy’s numbers and be quick to draw conclusions. Look at the stats that account for what normally goes unnoticed. Consider the player’s home ballpark and the status of league wide offense during his career. Use adjusted stats in debates with fellow fans about which of the all time greats was the superior player. When we talk about ERA+, another adjusted statistic, on Sunday, July 10th, be ready for my comparison of two Hall of Fame pitchers that will be sure to outrage any loyal Bethesda Big Train fan. Stay tuned!


Previous “Sunday Morning Sabermetrics” articles:

June 5th: Pythagorean W-L

June 12th: Wins Above Replacement


Next week (June 26th) on “Sunday Morning Sabermetrics”:

BABIP, ISO, and wOBA – be sure to catch next Sunday’s article on some of the statistics that further differentiate offensive performance, including Batting Average on Balls In Play, Isolated Power, and Weighted On-Base Average (mentioned earlier).

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