Sunday, January 20, 2013

No Agreement on Johnny Peralta as a Defender at Shortstop

Today, I'm going to revisit Tom Tango's Fan Scouting Report. Tango annually conducts a survey on defensive skills which many of you completed last year. For those of you who are not familiar with the survey, he asks fans to rate the fielding skills of players on their favorite teams just based on observation and instructed them not to use any stats at all. As you can see on the ballot, fans are asked to scout players on reaction/instincts, acceleration/first few steps, speed, hands, release/footwork, throwing strength and throwing accuracy.

Tango then tabulates the results which can be seen in detail on his site. Each player ends up with a score between 0 and 100 on each of the 7 skills. The league average rating for each of the 7 categories is 50 and a player with a rating of 70 or better is in top 16% in the league.

Tango also has a method for turning these ratings into runs scored above average. First, weighted averages are created for each player based on the importance of the skills at his position. The weights are shown on Table 1 below. I'm not exactly sure how he decided upon these weights but they make intuitive sense. For example, a third baseman's arm strength carries more weight than his speed. On the other hand, speed and acceleration are very important for outfielders.

Table 1: Weights for skills on fan fielding survey
Pos
Instincts
First Steps
Speed
Hands
Release
Arm Strength
Accuracy
C
1.3
0.3
0.3
1.3
1.3
1.3
1.3
1B
1.6
1.6
0.4
1.6
0.8
0.4
0.4
2B
1.6
1.6
0.8
1.6
0.8
0.4
0.4
SS
1.5
1.5
0.7
0.7
1.5
0.7
0.4
3B
0.9
0.9
0.5
0.9
0.9
1.9
0.9
LF
1.0
2.0
2.0
1.0
0.5
0.3
0.3
CF
1.0
1.9
1.9
1.0
0.5
0.5
0.2
RF
0.9
1.9
1.9
0.9
0.5
0.5
0.5

Once the weighted average is computed for a player, it is subtracted from the average score for all players at his position.  Adjustments are then made to make it comparable to the distribution of the Ultimate Zone Rating (UZR) statistic which has a smaller standard deviation.  For those who are interested in the details, the adjustments are explained in the comments here. I tried following that algorithm and got slightly different results (although very close) from what is listed on FanGraphs under FSR. The FanGraphs results are used in this post.

The results for past and present Tigers are shown in Table 2.  The table  tells us that there where 61 fans who rated center fielder Austin Jackson.  They gave him top 16% in MLB scores for instincts (84), first steps quickness (88), speed (86) and hands (79), above average scores on release/footwork (65) and accuracy of arm (55) and a below average score on arm strength (45).  This resulted in an average rating of 72 which translates to 8 runs above average.

Remember that these observations should be based on skills rather than performance. So, Jackson's score says that, in the eyes of fans, he has the skills to be a center fielder who is +8 runs above average in 1,184 innings (his total for 2012).  On the other hand, his +5 runs above on Defensive Runs Saved (DRS) is an estimate of his actual performance last year.

Table 2:  Fan Scouting Report for Tigers, 2012

pos
player
n
instincts
first step
speed
hands
release
arm strength
accuracy
FSR
C
Avila, Alex
47
52
40
33
56
67
63
63
2
C
Pena, Brayan
18
33
23
23
31
29
36
29
-4
1B
Fielder, Prince
55
32
20
25
25
25
36
31
-6
2B
Infante, Omar
47
70
65
61
63
65
49
63
+5
3B
Cabrera, Miguel
62
49
30
27
48
47
79
58
-3
SS
Peralta, Jhonny
56
46
32
36
62
59
51
61
-11
CF
Jackson, Austin
61
84
88
86
79
65
45
55
+8
RF
Hunter, Torii
19
75
70
61
75
77
70
77
+7
RF
Boesch, Brennan
52
10
23
38
11
22
45
35
-5
  
Table 3 compares the fan fielding estimate with other defensive measures.  For the most part, the Fan Fielding results for the Tiger players correlate reasonably well with the advanced measures. Players that did well on the advanced statistics such as second baseman Omar Infante, center fielder Austin Jackson and right fielder Torii Hunter - were also given high scores by the fans.  It should be noted though that Tigers fans rated Infante as average while Marlins fans had him well above average.

The fans and defensive statistics agreed that Miguel Cabrera was a a below average fielder, but his -3 on FSR was better than any of his other statistics.  There was universal agreement that right fielder Brennan Boesch was a poor defender.

There was more disagreement on shortstop Jhonny Peralta than any other player.  Peralta was rated worse by the fans (-11) than any of the advanced fielding measures.  Even the defensive metrics did not come to a consensus with Peralta ranging from -6 on Baseball Prospectus' FRAA to +10 on UZR.  There is some thought that DRS and UZR could be biased for some players due to human error in recording of location of batted balls.  So, perhaps the lower scores on FRAA and RZR might be more reliable for Peralta.

Why might the fans score be lower than all the metrics?  It could be that Peralta's skills were poor, but was able to perform above his skills for the year.  In that case, we might be wary about his ability to keep it up in 2013.  On the other hand, it could be that the fans are biased because he does not look athletic and that he's actually better than he seems.  We may learn more this year. 

Table 3: Comparison of Runs Across Different Fielding Measures

Pos
Player
FSR
DRS
UZR
FRAA
RZR
C
Avila, Alex
+2
+6
---
-3
---
C
Pena, Brayan
-4
+1
---
-1
---
1B
Fielder, Prince
-6
-4
-2
+1
+4
2B
Infante, Omar
+5
+6
+10
+4
+12
3B
Cabrera, Miguel
-3
-4
-4
-10
-18
SS
Peralta, Jhonny
-11
-1
+10
-6
-3
CF
Jackson, Austin
+8
+5
+4
+9
+11
RF
Hunter, Torii
+7
+15
+10
+1
+11
RF
Boesch, Brennan
-9
-8
-12
-5
-11



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