The 2007 Arizona Diamondbacks became just the third team in Major League Baseball history to win 90 games and be outscored during the regular season. Here are all three teams:
| 1984 New York Mets allowed 24 more runs than they scored |
| 1997 San Francisco Giants allowed 9 more runs than they scored |
| 2007 Arizona Diamondbacks allowed 20 more runs than they scored |
All three teams finished the season 90-72. The Mets finished second while the Giants won the NL West (like the Diamonbacks) but were swept in the first round by the eventual World-Series-Champion Florida Marlins.
It's remarkable that you can win that many games while being outscored. That's obviously why it has occurred so infrequently. As you might expect, the Diamondbacks led the majors with 32 one-run victories (against only 20 losses). As Bill James demonstrated, a superlative performance in one-run victories is an aberration and when the team comes back to normal in one-run games the next year, as most teams do, their overall record drops.
I don't know of any research that shows how well teams that won an inordinate number of one-run games fair in the playoffs; I would expect they might not perform as well. We'll have to take a look at that in the future.