Slyde was nice enough to solicit some questions ahead of time from various people. Here's one of mine and Nick's response:
RR: The Reds have made a few player personnel decisions over the last 6 months that appear to have been in favor of defense over offensive players. What has been the organization's reasoning behind these moves?
NK: Let's use Jay Bruce as an example. Bruce played centerfield last year. Jay Bruce statistically wasn't a great centerfielder, but he was good in right. So he goes from playing out of position to playing his normal position and Taveras comes in to play centerfield. If an average fielder catches 88% of the balls in centerfield and you get around 300-400 balls in centerfield, Willy Taveras is at 90% - he catches 2% more of the balls. So say he catches 8 balls a year more than the average, assuming Jay Bruce is an average centerfielder. If Willy is catching 8 extra balls, that's 8 extra at bats that we'll see. Two or three of the following hitters will get on base because of those at bats, so that's 11 total extra at bats that Willy has probably prevented. Now you add in the other guys that are out there (Bruce, Dickerson, Hairston, etc.) and compare them to the players that were previously out there and you could have upwards of 75 at bats saved in the outfield. We've got a flyball pitching staff - that's no secret. You may get 50 extra balls caught, but it's not just those 50 extra balls that matter. It's the .330 on base percentage after that plus the .330 on base percentage after that. It's not just those outs, but the effects of those outs on limiting the number of overall at bats.
If you are eliminating 75 at bats during the season, it means that fewer pitches are thrown, which means the starter can go longer in the game. If you look at the team in 2006, we had relievers who threw a lot of innings before the All Star break and then by the second half they were worn out or hurt. You are putting a lot of pressure on the relievers. So, improving the defense actually improves your pitching staff because you make more outs and you don't have throw as many pitches. You don't have to get a reliever up and sit him down as many times because the pitcher on the mound has things under control and so the reliever gets a real day of rest. That's where our defense has really improved in that way.
Ok, don't try to follow the math too carefully--this is a transcript of a verbal conversation, not a written argument. But I think the big picture point is right-on, and is something we've been talking about a lot: better fielding can have massive, pervasive effects on innings. I think we all know this intuitively when watching games, but many folk often seem to forget this when evaluating players. Now that we finally have some decent tools to assess defense, we can better understand how important it is.
Also, it's worth mentioning that the runs saved defensive estimates used here, on FanGraphs, etc, do take into account the "inning killer" aspect of better fielding that Krall talks about above in addition to just preventing a play. Tango has a nice discussion of this here.
Basically, the way it works is that the average single is worth ~0.5 runs. That's the additional runs scored you'd expect to get in an average inning that has a single vs. that same inning before the single. So, if you have a guy with excellent range in the outfield who prevents that single, you prevent that 0.5 runs. But in addition to preventing the single, you also caused an out! That extra out reduces the number of runs scored in an inning by, on average, 0.3 runs, because it prevents other players from coming up to hit as Krall describes above (Tango's "inning killer" component). So the total effect of the great play that prevents a single is 0.5 + 0.3 = 0.8 runs. This is where the shorthand 0.8 runs/play conversion that you'll sometimes see used comes from, though the one used in bUZR is specifically honed to the specific position, and I think also the zone, how hard the ball was hit, etc.
FWIW, the Reds' outfield currently sports a cumulative bUZR of +15.6 runs, which is on pace for +68 runs saved at the end of the year. Last year, outfield bUZR was -33 runs. In 2007, it was -31 runs. We're talking close to a 100 run difference (if they can keep on pace, of course), which equals ~10 wins. Don't get me wrong, I miss Dunn's bat...but I don't miss his glove, and I especially don't miss Junior's glove.
Congrats again to Slyde for scoring this interview! It's something he and I (and others) have talked about for a while, but to see it actually happen is really exciting! Hopefully it's just the start of a long, positive relationship between the Reds front office and the blogging community.