When we think about baserunning, we normally picture high-profile speedsters like Billy Hamilton or Mallex Smith. Yes, they may post an astounding number of stolen bases and runs scored, but do they really contribute the most to their team? The SPD score from Fangraphs attempts to classify not those who steal 70 bases in a season, but those whose mindset and speed on the basepaths allow them to capitalize on baserunning efficiency.
SPD is calculated on Fangraphs as a combination of stolen base efficiency, stolen base opportunities taken, runs scored percentage, and percent of triples. Obviously, this is not a perfect statistic. It's outdated in the way we measure runs created because it's on an arbitrary scale with 4.5 being the (estimated) average instead of using linear weights. SPD also doesn't factor in many important baserunning aspects like extra bases taken (XBT%) or movement when the ball is in play. While BsR is the more operative baserunning statistic nowadays, we must make do with SPD because it is available for minor league data whilst BsR is not.
Four prospects stood out from the rest in this category. Jorge Mateo, Wes Rogers, Kevonte Mitchell, and Leland Clemmons highlighted the top four of the listing, and all four are relative unknowns. So let's take a deeper dive into who these players are and why they set the record in SPD.
Starting at the top, Jorge Mateo ranks #1 in the minor leagues with a SPD score of 9.9. For reference, the highest SPD score in the MLB this year belongs to Dee Gordon with an 8.8. First off, we want to look at the scouting report because it may fill in some blanks. Baseball America writes, "Shortstop Jorge Mateo has louder tools, including 80 speed and a plus arm. He has a quick bat, works the count and uses the whole field, and takes advantage of his premium speed, stealing 49 bases in 69 games last year". When he signed with the Yankees for $250,000 back in 2011, he was known for being an incredible athlete with great speed, and the statistics back the report up.
Now let's see how he became the player behind the 9.9 SPD score. In his first season stateside with the GCL Yankees, Mateo played only 15 games and was then lost for the season with an undisclosed back injury. His one triple in 58 at-bats (1.7%) isn't great; however, Mateo did manage to convert getting on base 23 times into 14 runs (60.9%). This can be partially attributed to small sample size and the fact that baserunners only have slight control over their run-scoring ability; most control is derived from the batter. The main reason for Mateo's high score comes from his stolen base characteristics. In the 22 opportunities he's had to steal a base, he's attempted to steal 12 times, making for an outrageous 54.5% stolen base frequency*. Not only did he attempt to steal 54.5% of the time, but he also succeeded in stealing a base in 11 out of 12 tries, or 91.7%. For perspective, if minor league plate appearances leader Daniel Robertson (642 PA) attempted to steal 54.5% of the time possible and succeeded in 91.7% of the times he tried, he would have 120 stolen bases.
You'll notice that as we slide down to player number four, each player's notoriety generally decreases. Next up, Wes Rogers, the Rockies' 4th round pick in the most recent MLB draft, comes in tied for second with a SPD score of 9.8. Signed for $360,000 out of Spartanburg Methodist JC, Rogers was known for his high-profile speed and excellent plate discipline. Baseball America reports that Rogers is "an exceptional athlete and... at least an average runner who is better under way". His skills obviously translated well from college to the MiLB, where he maintained a .357 wOBA over 131 plate appearances at Rookie level Grand Junction.
Statistically speaking, Rogers' two triples in 113 at-bats (1.8%) is on par with Mateo's, and he managed to convert 43 times on base into 22 runs (51.2%). Both scores rival the leader, and like Mateo, Rogers created his value by wreaking havoc on the basepaths through stolen bases. He had 41 opportunities to steal a base, and he attempted to steal 16 times, resulting in a 39.0% stolen base frequency. Even though he was less aggressive in base-stealing than Mateo, Rogers was more efficient at converting. He succeeded in stealing a base 15 times in 16 attempts (93.8%). Using the same Daniel Robertson comparison, Rogers would have stolen 88 bases, good enough to tie for first in the minor leagues.
Kevonte Mitchell, the next player on the list, is actually tied with Wes Rogers for second place with a 9.8 SPD score. The Cubs' 13th round pick from the 2014 MLB draft, Mitchell was known for being an athletic and toolsy player who could handle third base. The Cubs decided to scratch the infield possibility completely and start anew at center field for Mitchell, who quickly proved he could handle the position if given more time. Nathan Rode of Prep Baseball Report described him as being "very raw" and having "thunder in the bat" with quick hands. Not much of a scouting report, but that is the norm for most young high schoolers going through the draft process.
Out of all four players here, Mitchell probably had the most productive season, batting .294 while creating runs at a 20% above league average rate. The amount of triples rarely influences the SPD score because there is such a minor difference between one player and the next; however, Mitchell ran out four triples in just 143 at-bats, good enough for one about every 36 at-bats (2.8%). Additionally, he was able to turn 61 times on base into 30 runs (49.2%). His forte happened to be stealing bases - not the powerful bat he was described as possessing. In 57 possible chances, Mitchell attempted to steal on 20 of them (35.1%) and succeeded every time but one. 19 stolen bases to 1 caught stealing (95%) is an amazing ratio and much more than necessary to be productive. Like Mateo and Rogers before him, Mitchell would have stolen many more bases given the opportunities; the Daniel Robertson comparison would have Kevonte stealing 80 bases.
Last on the list, I can almost guarantee you haven't heard of Leland Clemmons. Signed by the Royals out of Winston-Salem State University in the middle of the season and assigned to Burlington, he was reportedly brought in because of his speed and defense. His bat has many question marks and the .224 batting average only further muddles the picture. His coach in college, Kevin Ritsche, stressed his speed by saying, "he ran a 60-yard dash faster than anyone at tryout" (Reportedly ran a 6.20). Funny enough, Clemmons played in an exhibition game this summer against the Burlington Royals for a summer collegiate team.
Down on the sabermetric front, Clemmons impresses in the speed area even if his bat isn't quite ready. He hit one triple in 85 at-bats (1.2%) and turned 30 times on base into 14 runs (46.7%). Both numbers put him in good company at the top of the leaderboard. Clemmons had 29 opportunities to steal a base and ran on 14 of them (48.3%), only being caught once (92.9%). The final part of the process pits Clemmons on an extrapolated journey over 642 plate appearances, where he steals 108 bases.
So, what did we learn? Well, hopefully this was at least fun look at some great stolen base ratios and run-scoring production. There were many flaws with the process though. Most people probably expected a speed artist like Jose Peraza on top of the list, and to tell the truth, someone more prolific like him most likely deserves it. SPD does have some deep-rooted problems that cannot be solved without a permanent switch to BsR. Small sample size and extraneous factors confuse the statistic and can lead to unlikely scores. At this point in time, SPD has become an outdated statistic that can't be reliably used to measure player development or accurately determine their baserunning acumen. If only more data tracking systems would be implemented in the minor leagues. Imagine the possibilities.
*Note that Stolen Base Frequency is not a calculable statistic from minor league data and this calculation is more of an estimation of when the player could steal and assuming the base ahead of him is always open.
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