Pitching and fielding together is half the game, hitting being the other half. Actually, because in the long run good pitching/decent hitting wins more ballgames than good hitting/decent pitching, the pitching and fielding is slightly more than half. Why is it better? Well, if your starters allow less baserunners, they should throw less pitches, and if they throw less pitches, they should be able to throw more innings before they reach certain pitch counts. That in turn means less bullpen innings, which means that your relievers, on top of having better defence behind them, ought to be fresher, which gives you more effective pitching options, which can help you prevent further runs. If your starters and fielding is effective enough, you may not be able to find work for everyone in your bullpen, so you may be able to run with less pitchers on your staff, so you can have more bench options, which means more in-game flexibility, which, if exploited by the manager, can mean more runs for the offence, or still even better defence and less runs allowed. Furthermore, a pitcher that trusts his defence can be more effective at doing his job as a pitcher, partially because the confidence of his effective fielders rubs off on him, partially because there's no ineffective fielding to rattle him, partially because effective fielding can inspire him to raise his own game. An effective pitcher is often confident in himself too, and therefore better able to get over poor pitches, innings and outings, because he trusts himself and his own ability. Finally, an effective and efficient pitcher that throws less pitches is theoretically less likely to get injured or wear down as the season goes on, and fielders are less likely to get injured because there are less plays to make in the field and they spend less time in the field, which is less sapping for them too, especially catchers. The less tired your best players are the less off-days they need. And so on and so on and so on. Or, in other words, look at the Rockies. First, for an individual game: If your offense is that much incrementally better, the exact same effect happens to the other team. You get their starters out of the game that much sooner, getting to the soft underbelly of the opposing pitching staff, leading to even more runs. Which leads, of course, to even more victories. Since it works both ways, I'm not sure I'm convinced that P&D is inherently worth more than O. Unless you're arguing that an incremental increase in offensive talent gives a linear increase in runs scored, while an incremental increase in p&d talent gives an exponential (or at least non-linear) increase in runs allowed. For the long haul: The effect of being in the field more during the year may lead to more injuries, wearing down, etc., but my thinking is that this would be a small enough effect that it wouldn't be statistically significant. But that's a pure matter of opinion. Have there ever been any data-based studies that showed that denying runs is a more effective winning strategy than scoring them?