There are five tools scouts look at when evaluating a baseball player; speed, hitting, power, arm strength, and defense. Many of these tools can be partially evaluated through statistics; with immediate figures like batting average and slugging percentage available across all levels of baseball. Visually, it is usually immediately clear who the fastest runners on the field are, whether they are getting to balls destined to be hits or stealing bases despite desperate throws from the opposing catcher. These players usually bring an air of excitement onto the field that eventually leads to them being fan and highlight reel favorites. However, the effect this speed actually has upon the run output of both teams is an intricate question. This is not a question of isolated hitting or power prowess, in which the subsequent scoring effect can be broken down through simple statistics, but instead a deeper mystery. Determining the true value of this tool is not easy, and strides toward an understanding of the value of speed could help teams place proper value on how much players with this innate trait can impact a baseball game.
The steroid era put emphasis on hitting baseballs as far as possible, with less regard for stolen bases and defense. It would stand to reason that with these juiced-up hitters being gone, teams would place a premium on players that have speed, trying to spark teams on both offense and defense. This does not appear to be the case, as speed seems to be a tool that has not been valued as highly as others, such as power, by Major League teams. In my first article for AnalyticsGame, I presented an argument that was incomplete. In looking at how stolen bases affected scoring runs, I had determined that stolen bases by themselves had little effect on the run output of a given team, deriving the conclusion that speed may not have as great an impact on run production as previously thought. The correlation of stolen bases to runs scored over the last ten years returned an R-value of 0.1, insignificant albeit positive. Mistakenly, that was judging the value speed solely in the isolated activity of stealing bases. To begin to analyze the holistic offensive effect of speed, we must start from the beginning and look at how speed impacts reaching base.
In order to steal the next base, a player must have already reached base safely. While speed does not significantly affect how much a hitter walks, it does have an effect on how often they reach base when putting the ball into play. Using data spanning the last five years from FanGraphs, I looked at the relationship between speed and BABIP, or batting average on balls in play. BABIP is a statistic that measures how often a player gets a hit when putting a ball into fair territory, taking home runs and strikeouts out of the equation. The average BABIP of all players is usually consistent on a year-to-year basis, indicating that hitters have little control over a ball after putting it in play. In order to determine how speed can influence BABIP, I used FanGraph’s “Spd” statistic. While a bit outdated, this figure combines certain aspects of a player’s performance into a metric that estimates their speed, with incremental measures from awful (2) to excellent (7). The average BABIP of players with a speed rating of “average” or below was 0.279 while the average BABIP of players with a speed rating above “average” was 0.302. This means that runners with speed above “average” are reaching base much more frequently on balls they put in play, which equates to almost 14 more hits over the span of a 600 at-bat season. Furthermore, hitters with speed ratings above “excellent” had an average BABIP above 0.312, which equates to almost 20 more hits than the average runner would attain. This validates what many fans see while watching a baseball game, that quick runners have a much better chance of reaching base on hits such as ground balls, and can help quantify this effect over the span of a season.
Now that there is an estimate of how speed helps getting on base, the discussion of how it helps while on base can continue. Stolen base totals may not have been the best measurement of base path efficiency to use in my previous analysis. A more telling figure, known as wSB, gives weight to base stealing to depict how many runs a player’s base stealing efficiency has been worth. The league leader last year, Jose Altuve, was worth 7 more runs than the average player based on base stealing alone. This shows how base stealing can, in fact, significantly impact run scoring. Using a similar analysis as before, comparing “Spd” to “wSB”, speed clearly impacts runs derived from base stealing. While average and below average runners have little effect, players with great and excellent speed ratings have average wSBs of 2.3 and 3.1 per 162 games respectively. This means the average players in these two speed tiers are creating 2 or 3 more runs for their teams than the average runner from just their base stealing activities alone. The most skilled base-stealers can create as much as 10 more runs. While these may seem like small numbers, these manufactured runs are invaluable in an era where run-scoring is down. These estimates may also be conservative as wSB does not provide context, such as catcher skill or situation, but still show how base stealing is putting fleet-footed runners at a run-scoring advantage compared to their stagnant counterparts. This, combined with their increased likelihood of getting hits, should be understood by every Major League Baseball team as they try to contextualize the advantage that speed can give to their offensive output.
While there are indirect indicators of speed’s impact on offense, the numerical effect becomes even less clear when looking at defense. There are far less definitive statistics for defensive prowess as it is not something usually measured in numbers like hits or stolen bases. Many defensive statistics are indicators that provide estimates of defensive value such as range based on batted ball predictions. Estimates are usually not the best way to derive concrete conclusions, as they usually are presented regressed closer to the mean, but they can still be used to show the value of speed. When looking at all players, there is no correlation between speed and defense. This can easily be dismissed because immobile players like catchers and first basemen are included, positions where a player can be an elite defender no matter their speed. When this statistic is broken down to just outfielders, where speed and range can make the most significant defensive impact, there is a clear correlation between speed and defensive ratings, with a value of 0.62 which indicates a strong linear relationship. This can be analyzed further to attribute almost 4 runs above average per 162 games for every one point increase in speed rating. This means a player like the Brewers’ Carlos Gomez could theoretically be worth 24 more runs saved defensively than a player like former Padres outfielder Carlos Quentin over the course of a season. Defensively, as it pertains to the outfield, speed can make all of the difference for these players to create significant value in terms of runs saved for their teams.
This quantification of speed can provide important insight into evaluation as basis for comparison to other tools such as pure hitting and power. Speed can complement a hit and defense tool, making a player significantly more proficient in both of these areas, and allow a player to wreak havoc on the base paths. While base-stealing alone may not be the best way to properly evaluate speedy players, there is still marginal value in terms of runs derived from base stealing. In an era where runs are at a premium, even this 5 to 10 run predicted value can make a huge difference in terms of one player. Additionally, the value speed has shown in terms of reaching base is somewhat eye-opening, and the defensive value it can provide seems invaluable.
Speed alone, however, cannot guarantee future success. A track runner who has never played baseball should not be drafted with the expectation of stardom. In conjunction with other tools, it can provide a significant advantage for a player, but if a player cannot hit or does not understand the game of baseball, this speed advantage can quickly be neutralized. Speed should be viewed as supplemental tool; one that a player can use to create surplus value on top of their other tools. It can turn a 0.280 fringe hitter into a 0.320 table-setting All Star. It can turn a defensive liability into a Gold Glove winner. Speed can provide an avenue to stardom for players that have other foundational skills. This data bodes well for upcoming fleet-footed centerfield prospects like Byron Buxton of the Twins and Travis Jankowski of the Padres. These players are in the position to become stalwarts, beginning in 2016, in the outfields of their teams because of their abilities to combine their speed with power and hitting tools, respectively.
In this era, where runs are scarcer than ever, manufactured offense and runs that are saved on defense should be valued very highly. As defensive statistics begin to improve, with technologies like MLB’s recently debuted StatCast, perhaps more clarity will arise in terms of how much speed is truly affecting defense, and a more accurate value can be attributed. Presently, even these conservative figures are supporting the value of speed in player evaluation. Perhaps as teams adapt to the powerless times, they will begin to adopt strategies that powerhouses like the Royals and Cardinals have, finding players in a position to take advantage of their speed, to create a roster that consistently frustrates opposing teams. Speed alone is not going to make a championship team, but the comparative advantage it seems to give players, specifically outfielders, is something that baseball teams should understand, and possibly start placing more value upon.