Question: How does the fielding of 2nd and 3rd baseman compare to when they play the opposite position?
Why I asked the question: Mark Teahen of the Royals is being asked to practice at 2nd base for the up coming season. Using other players as comparison, how should Mark project at 2nd.
Analysis: I used UZR as the defensive metric which is available at Fangraphs.com. UZR is the best freely available defensive metric I can find. As with any defensive metric, it is far from perfect, but for now it is the best to use. I looked at all players from the last 3 season that played at least 100 innings at both 2nd and 3rd base. I came up with 43 players. To equally weight the weight the at bats I determined the Harmonic mean in at bats between innings and UZR at 2nd and 3rd
Harmonic mean =2/((1/innings at 2nd)+(1/innings at 3rd))
Note: I had a discussion with Tom Tango on his blog on the best way to measure the differences.
I then added the UZR and innings for all players at 2nd and 3rd and got the following results:
Average UZR/150 games at 2B: -1.90
Average UZR/150 games at 3B: -0.85
Then I group the the players that played the majority of time at 2B and got the following results
Average UZR/150 games at 2B: -1.73
Average UZR/150 games at 3B: -0.49
Finally I group the the players that played the majority of time at 3B and got the following results
Average UZR/150 games at 2B: -2.21
Average UZR/150 games at 3B: -1.49
There are the general numbers showing how it seems that 2nd base is harder to play than 3rd base for this group of players over the last 3 years.
Lets take this data and extend it further to see how it effects the Royals and the decision to move Mark Teahen to 2nd. From the above data, we can determine that Mark then should see a change of -1 UZR/150 from his lifetime 3rd base average (-11.6) to -12.6, which would make him the worst defensive 2nd baseman when comparing his -12.6 UZR/150 to all 2nd baseman with over 400 innings played last year. So if Mark played 2nd base for 150 games next season, his defense would cost us 15 runs compared to your average defensive 2nd basemen.
Callaspo on the other hand rates at 5.9 UZR/150 at 2nd base. Using a Run Generator calculator to determine the difference, the Royals will score 6 more runs with Teahen in the lineup vice Callaspo if they were each to play 150 games at 2nd. As a whole, the Royals are -12.5 runs worse as a team if they were to play Teahen at 2nd vice Callaspo, or ~1 win.