You, too, can be a scoutby John Walsh
January 28, 2008
Could you be a baseball scout? Can you judge baseball talent by watching somebody play? Why not? Many serious fans watch 100 or 150 baseball games a year; surely they must learn something during all those hours. As Yogi said, "You can observe a lot just by watching."
Well, as many of you probably know, occasional THT contributor Tom Tango believes that fans do know how to judge talent, and he also believes in the wisdom of crowds, meaning that if you ask enough people a question the average answer will be pretty good. The result is Tom's Scouting Report, By the Fans, For the Fans.
The Fans' Scouting Report
Basically, Tom asked fans, anybody who wanted to contribute, to rate the defensive abilities of major league players. He wanted people who had seen the player in question in at least 10 games during the 2007 season and asked for a judgment in seven different defensive categories, which I list here:
- Before/As ball is pitched:
- While ball is in air/on ground
- Acceleration/First few steps
- Velocity/Sprint speed
- After ball is caught (throwing)
- Throwing strength
- Throwing accuracy
Oh, one more important thing: Tom specifically requested that people not take any stats into consideration when evaluating fielders. Let's take a look at an example:
Guerrero, Vlad Instincts FirstStep Speed Hands Release Strength Accuracy 48 43 50 26 67 93 58 Ballots Agreement Overall 29 0.65 52Twenty-nine fans gave their opinion on Vlad's defense and the agreement level of 0.65 is roughly typical. He scores above average in the three throwing categories (especially "Strength"), but poorly in "Hands" and below average in "First Step." Tom calculates an overall, position-neutral score from the individual categories and Vlad scores 52, just about average.
Cool, no? This is undoubtedly a great resource, but I have one question: Can it possibly work? I don't doubt that fans can recognize good (or poor) play when they see it, but we fans are also clearly influenced by a host of factors that go beyond observation: reputation; past, perhaps out-dated, performance; our own prejudices, including bias towards our favorite team and players; knowledge of defensive stats; and probably others that I haven't thought of.
Another issue is how well fans/scouts can actually observe players. I'm guessing that many of these fans are watching games on television—how can they judge "first step" or "instincts" when watching on TV? You have to be watching the player before the ball is hit to judge those things. And even if you are at the park: are you going to be staring at J.D. Drew as the pitcher delivers the ball? You'd have to do that for every pitch in a game in order to see his reaction to the handful of balls hit his way in a game. Who watches a game like that?
So, "first step" is not so easy, but how about throwing? The throw is always captured on TV or by the fan at the ballpark. Furthermore, it's fairly easy to judge arm strength and while "release" and "accuracy" are a bit trickier, if you pay attention, you can judge these aspects of throwing as well. So why don't we have a look at how the fans/scouts rated throwing and see if their observations agree with the numbers?
Enter the stats
What numbers, you ask? Well, I happen to have some results on outfield throwing handy, so we can compare those numbers to the fans' report. The first thing to do is to combine the three throwing categories of the fans' report (remember, release, strength and accuracy) into a single arm rating. I'm going to do the easiest thing and simply average the three values. Here are the top 10 outfield arms (any outfield position) according to the fans' report:
10 Best OF Arms, Fans' Scouting Report 2007 Name Arm Score Young, Delmon 92.7 Suzuki, Ichiro 91.3 Victorino, Shane 91.3 Francoeur, Jeff 88.3 Cuddyer, Michael 87.0 Rios, Alex 84.0 Hawpe, Brad 82.7 Hamilton, Josh 82.3 Markakis, Nick 81.0 Pie, Felix 79.0and here are the trailers (I am merciful, so I only list five):
Pierre, Juan 7.0 Podsednik, Scott 9.0 Bay, Jason 17.7 Damon, Johnny 17.7 Owens, Jerry 20.3 Gibbons, Jay 20.7
If you look back at my article on 2007 outfield arms, you will see some agreement. My top five right field arms were: Cuddyer, Francoeur, Young, Victorino and Rios. Wow! These are exactly the first five right fielders in the fans' report (although not in the same order). I also had Pierre and Owens as atrocious, Bay was around average, but poor in previous seasons. Damon and Podsednik did not qualify in 2007, but both have been terrible overall in recent seasons. Gibbons has been about average over the past few seasons.
Hey, this is looking pretty good, so far. How about my top five center field arms? Here they are, along with their ArmScore from the Fans' Report:
Top Five Center Fielders, according o statistical analysis Name Arm Score Upton, BJ 57.3 (scouted as 2B) Taveras, Willy 49.7 Edmonds, Jim 77.7 Suzuki, Ichiro 91.3 Freel, Ryan 39.3Uh, oh. Not so good, is it? Taveras and Upton are rated as average-ish, while Freel is definitely seen as below average. Ichiro, considered to have the second-best outfield arm in baseball by the fans, only manages fourth place in my center field ranking.
Hmmm, looks like we're going to have to dig deeper to see what's going on. Instead of looking at individual results, let's widen our perspective a bit. The plot on the right shows how well the results from my outfield arm analysis match up with the Fans' Report. Each point represents a single outfielder season (between 2005 and 2007), with his Fans' Arm Score plotted on the horizontal axis and his runs saved per 200 opps (my analysis) on the vertical axis. I require at least 50 opportunities in a given season and (of course) only outfielders that have a scouting report are plotted.
I don't know what you think, but in my opinion that's an ugly plot. Oh, we do see some agreement—if you squint your eyes and tilt your head slightly, you can see an upward slope to the mass of points as you move to your right. But I was expecting a tighter bunching of the points around a straight line. To quantify the agreement, it's customary to quote a correlation coefficient: it turns out to be 0.39. That is not a strong correlation.
Proceed with caution
But, you have to be careful with correlation coefficients, as Tom Tango himself likes to forcefully point out. What I think is happening here is that there is too much noise in the statistical analysis. Brad Hawpe, who ranked high in the Fans' Report, scored 2.7, 11.2 and -4.4 runs per 200 opps from 2005 to 2007. Ichiro had years of 10.6, -1.2, 8.9 and 5.2 (2004-2007). Now, some of the variation may well be due to other factors, but a large part of it is likely statistical noise.
We can try to reduce the effects of noise by increasing the minimum number of opportunities—the more opportunities you consider, the closer you can get to a player's true talent level. The graph on the right shows how the correlation coefficient between runs200 and Arm Score varies as we increase the minimum number of opportunities. To beef up the sample size for this plot, I combined all results for the three-year period 2005-2007, and furthermore, I combined results from the three different outfield positions if a player played multiple positions in that time frame.
As expected, as we move to more and more opps, we see a stronger correlation (the rising blue line) because there is less noise in the data. The red line shows the number of players that meet the minimum opps requirement. The point here is that there is a strong correlation between the statistical analysis and the scouting report. For example, when at least 500 opps are required, the correlation coefficient rises to 0.78.
So, why don't we go back to our original plot of runs200 vs. Arm Score, but this time we use the combined data and ask for at least 300 opportunities for any given player. This gives me 70 outfielders to look at. Here's the graph:
Compared to the original version above, here we can see a strong correlation between runs200 and Arm Score. I've superimposed the "trend line" that best describes the data. Note how the trend line comes very close to intersecting the point (50,0). In other words, an average Arm Score (50) is predicting an average runs200 (0). This is impressive agreement — there is nothing that I've done here that forces the line through that point. This is the wisdom of crowds at work.
I've annotated a few players who have performed much better (in green) or worse (in red) than what the scouts would have predicted. I just picked these by eye, but for those of you who like numbers, here is a list of the players who exceeded the scouts' expectation by the greatest amount.
Most Underrated by Fans/Scouts ArmScore Pred. Actual Difference Soriano_Alfonso 73.0 2.6 11.1 8.6 Cuddyer_Michael 87.0 4.2 11.2 7.0 Taveras_Willy 49.7 -0.3 5.7 5.9 Francoeur_Jeff 88.3 4.4 9.8 5.4 Jones_Jacque 21.0 -3.7 1.6 5.3 Ramirez_Manny 54.3 0.3 5.6 5.2 Floyd_Cliff 30.3 -2.6 1.9 4.5 Lofton_Kenny 29.7 -2.7 1.2 3.9 Ibanez_Raul 32.3 -2.3 1.1 3.5 Rowand_Aaron 44.7 -0.9 2.5 3.4 --------------------------------------- Pred: predicted runs200 from trend line Actual: actual runs200 Difference: Actual - Predand here are the underachievers:
Most Overrated by Fans/Scouts ArmScore Pred. Actual Difference Green_Shawn 32.7 -2.3 -8.8 -6.5 Drew_J.D. 62.3 1.3 -4.5 -5.8 Anderson_Garret 58.3 0.8 -3.7 -4.5 Giles_Brian 46.0 -0.7 -4.6 -3.9 Griffey_Jr._Ken 64.0 1.5 -2.2 -3.7 Clark_Brady 38.7 -1.6 -5.0 -3.5 Gathright_Joey 28.0 -2.9 -6.1 -3.2 Jenkins_Geoff 76.0 2.9 -0.1 -3.0 Kearns_Austin 73.7 2.6 -0.2 -2.9 Dye_Jermaine 57.7 0.7 -1.9 -2.6
What makes for a good thrower?
Since the scouts have done a good job of evaluating arms, might we look at the individual components of arm rating, i.e., strength, accuracy and release, to see if we can learn something about the relative importance of these aspects?
Well, the short answer is "no." The reason is that when you look at these three categories, you find that there is a strong correlation between any pair of them, as you can see in the graphic below (which includes all outfielders in the Scouting Report).
I believe fan bias is playing a role here, because I doubt that the real correlations are as strong as we are seeing. Furthermore, in the case of strength vs. accuracy, I might have expected to see little, or even negative, correlation, not the strong positive correlation we see in the plot.
What I guess might be happening is that fans are able to judge a player's overall throwing skill, but they tend to give a good thrower high scores in all three categories and conversely for poor throwers. They are not able to judge independently the three different throwing categories. That's my hypothesis anyway.
In any case, the high correlations among the arm categories makes it impossible to determine the relative importance of strength, accuracy and release in evaluating outfield arms.
The Fans' Scouting Report, while not perfect, is a great resource, and I believe it will be a useful piece of the puzzle in understanding defensive ability. When you see Tom's invitation to participate in the 2008 Scouting Report, do not hesitate to do so.
John Walsh dabbles in baseball analysis in his spare time. He welcomes questions and comments via e-mail.