The Myth of Wells in RF: Rebunked!!!

Recently, a fanpost by Sivvi raised the question of whether moving Vernon Wells to RF would actually be beneficial to the Blue Jays. He came down in the negative, saying Vernon would not be a very good defensive rightfielder and that, even if he was, the bump in defensive value was overstated by many BBB commenters (including me).

I decided to investigate the matter and determine whether there is actually a bump in defensive stats by moving from CF to a corner position and how large that bump is likely to be.

Herein, I provide my analysis.

Defensive metrics are fairly new to the SABER community and are generally known as less refined and somewhat less reliable than the older offensive metrics. For example, different offensive WAR calculations generally agree on which players are good hitters relative to others, even though they might assign different WAR values to those players. Different defensive metrics, however, often vary widely (DRS vs. UZR, e.g.). One reason for this is that defensive metrics have been acknowledged as requiring larger sample sizes than offensive ones to arrive at reliable conclusions and predictions.

With that said, I first set out to collect my data samples. My starting sample included all players who qualified for the batting title outfield, as determined by searching fangraphs.

I included in the study only examples in which the player played 140 or more games at a given OF defensive position (e.g. if a player had 500GP in LF, but only 120GP in CF, no dice). Yes, 140GP is an arbitrarily selected value, but I felt it was large enough to give decently representative data but small enough to allow a large enough number of players to be analyzed.

The following 2010 MLB OF qualifiers were thus excluded due to insufficient data:

Crawford, Holliday, Soriano, Ibanez, Braun, D. Young, J Gomes, C Lee, Bruce, J Upton, Heyward, Francoeur, Pence, Choo, Ludwick, Swisher, Bautista, Markakis, Hart, Ethier, Hamilton, Torres, Carlos Gonzalez, Pagan, C Young, Bourn,  Vernon, Austin Jackson, Granderson, Rasmus, Hunter, B Upton, McCutchen, Stubbs, Span, Adam Jones, R. Davis, Fowler, Morgan

My first analysis looked at career UZR/150 of players who had played >140 GP at either corner OF position AND >140 GP in CF. Note that UZR incorporates calculations of the players’ arm values, so the difference in the relative importance of throwing arm strength at LF, CF, and RF are accounted for in this analysis.

Here are the results, player by player, for players who were listed on fangraphs as corner outfielders for 2010 and also met the career inclusion criteria for CF:

1. Brett Gardner

LF (140 GP):   +39.2 UZR/150

CF (165 GP):   +22.4

Net change moving from CF to corner OF position: +16.8 UZR/150

2. Juan Pierre

LF (327):         +7.7

CF (1192):       +5.7

Net change:      +2.0

3. Scott Podsednik

LF (545):         +0.3

CF (379):         -5.4

Net change:      +5.7

4. Ichiro Suzuki

RF (1294):       +13

CF (265):         +7

Net change:      +6

5. J.D. Drew

RF (1191):       +7.3

CF (220):         -2.3

Net change:      +9.6

Here are the players who qualified at centre field in 2010 according to fangraphs but have also played >140 games at either corner OF position.

1. Marlon Byrd

LF (142):         +6.9

CF(679):          -1.5

Net change:      +8.4

2. Alex(is) Rios

RF (720):         +12.9

CF (283):         +5.8

Net change:      +7.1

3. Shane Victorino

RF (146):         +19.6

CF(523):          +3.7

Net change:      +15.9              

4. Franklin Guitierrez

RF (213):         +23.0

CF (328):         +19.0

Net change:      +4.0    

5. Cody Ross 

RF(214):          +2.0                

CF(358):          +0.2

Net change:      +1.8

6. Matt Kemp            

RF (168):         -5.9

CF(452):          -10.8

Net change:      +5.9

7. Melky Cabrera     

LF(266):          -2.3

CF(416):          -7

Net change:      +4.7

Each one of these 12 players has seen an increase in his UZR/150 value when playing a corner OF position relative to playing CF. The analysis covers players who started in a corner and switched to CF (Guitierrez, Rios, Victorino) and players who started in CF and then moved to a corner (Pierre, Gardner). It includes good fielders (Guitierrez, Ichiro, Rios) and bad fielders (Kemp, Cabrera, Podsednik). Even with the generally accepted truism that players play CF during those portions of their careers when they are more skilled and corner OF when their skills are less developed or have declined, each of our players of them saw an increase in UZR/150 at the corners versus CF.

How substantial was this increase? The lowest such increase was +1.8, with the highest being +16.8. The non-weighted mean increase was +7.2 UZR/150, worth about two-thirds of a win over a season (assuming we replace this player in CF with a defender of similar skill). Remember that this value accounts for the relative value of arm strength at each position. I would render this a substantial increase in defensive value simply from moving to a corner from CF.

So far we have only looked at a player’s career numbers. Maybe there is some confounder hidden in that data that makes our analysis of career numbers baseless. Maybe we need to analyze the data comparing eras of players’ career when they are, presumably, of similar skill level to see how their fielding values change. So let’s do that.

In this portion, I looked at situations when players changed positions mid-career. Inclusion criteria were 140GP at any of the 3 OF positions in a single season or a combination of the 2 or more consecutive prior seasons. For the 2 prior seasons combinations, I used the average UZR/150 weighted by games played to arrive at the players’ true skill level

Here, are the players who qualified for the batting title at an outfield position in 2010 and had a collection of seasons as described above:

1. Scott Podsednik

Season             Pos      GP                   UZR/150

2003/2004       CF       123/153           -11.9/+2.3 à -4.0

2005/2006       LF        124/135           +2.2/+8.1 à +5.3

Net change: +9.3

2. Alex Rios

Season             Pos      GP                   UZR/150

2008/2009       RF       93/110             +23.8/-1.5 à +10.1

2010                CF       143                  +3.8

Net change: +6.3

3. Ichiro Suzuki

Ichiro has played 1 full season of CF, in 2007.

Season             Pos      GP                   UZR/150

2005/2006       RF       158/121           +4.1/+22.3 à 12.0

2007                CF       155                  4.8

2008/2009       RF       91/145             4.8/8.8 à 7.3

When Ichiro moved from RF to CF in 2007, he saw a net change of -7.2 UZR/150. When he moved back, he saw a net change of +7.3. I will concede that in Ichiro’s first season after returning to RF from CF, he had the same UZR/150 as his CF full season, but this was in only 91 games played. Using our 2 season combination method, he saw an increase of +2.5 in his move back to RF. It should be noted that his numbers have continued to climb since going back to RF, as he won a Gold Glove this year with a UZR/150 of 14.8 in RF.

4. Franklin Guitierrez

Season             Pos      GP                   UZR/150

2007/2008       RF       88/97               +17.3/+33.0 à +25.5

2008                CF       153                  +28.9

Net change: -3.4

Guitierrez actually saw a decline in his rating at his switch from RF to CF using our 2 season combination method. If we took his 97 GP season from 2008 as representative, though, he did see a decline. Nevertheless, adhering to our inclusion criteria, we must credit Guitierrez with a decline in UZR/150 after he moved to CF. I would posit, though, that Guitierrez is one of the best young (and best overall) OF in the game, and has been making phenomenal strides to improve his already amazing defense each season. Given the change to play full time in Seattle in 2009, he made the most of it and his true talent came out to shine. I venture that had he played RF in 2009 (he couldn’t because Ichiro was there), his UZR/150 would have been higher than his amazing +29.

Though this analysis is somewhat more equivocal than the career statistics one, we still saw improvements in UZR/150 in 3 of the 4 players we analyzed when they moved from CF to a corner OF position over the course of one season. The only player who actually had a better rating in UZR/150 is an up-and-coming defensive star in his first full season as an outfield (Guitierrez had never played >100 games in a season prior to 2009). The year-over-year analysis also supports my assertion that we can expect an increase in defensive value from moving Wells from CF to RF, and that this improvement is not trivial.

Several other players showed increases in their UZR/150 in corner OF positions relative to CF, but missed our inclusion criteria. These include:

Melky Cabrera: Lost 16.9 UZR/150 moving from LF (116GP) to CF (131) in 2007.

Josh Hamilton: Gained 34.1 UZR/150 moving from CF (111) in 2008 to LF (92) in 2010. Note that he missed 2009 with injury.

Shane Victorino: Lost 14.5 UZR/150 moving from RF (114) to CF (149) in 2008.

Andres Torres: In 2010, played 37 G in LF (53.7 UZR/150), 82 in CF (12.4), 43 in RF (33.4). Substantially better at the corners.

I believe that these analyses demonstrate that players on average see increases in their UZR/150 ratings worth at least 0.5WAR in moving from CF to a corner OF position. This supports my contention that we should move Wells to RF, assuming a suitable CF replacement can be found.

I now invite you to tear apart my work.