Intuition would suggest that if you scored more runs than you allowed, your win loss percentage would be better than .500. Unless you're the Oakland As this year. Then you're 13-18, despite the fact that you've scored 140 runs on the season and allowed only 136.
Stranger things have happened. But this usually occurs when a team bunches its runs in a handful of "blowouts," and then loses a number of "close" (one and two-run) games.
Take the case of their ace, Dallas Braden, who has a 2.79 ERA. With those kinds of numbers and say, New York Yankees run support, he could be posting wins like Chien-Ming Wang (the former one, anyway). Nineteen wins a year, no problem. The real question would be over or under 25.
Braden's 3-4 this year, however, because he pitches for the Oakland As. His three wins have included scores of 8-2, 5-2, and 4-2, or a total of 17-6. In his four losses, he's been outscored 14-3. He (and his relievers) gave up an average of 2.0 runs per game in his wins, and 3.5 runs per game in his losses.
That's a difference certainly, but not a huge one, going "from top to bottom." But Oakland hitters have scored an average of 5.67 runs in his three wins, and 0.75 runs in his four losses. That's the real difference.
A similar story could be told of Trevor Cahill's four decisions: two wins of 12-3 and 9-4, and two losses of 8-2 and 1-0. He deserved to lose the game in which he gave up seven of the eight earned runs. But not the one in which he pitched seven innings of one-run ball.
So where should that As be if their actual results reflected those suggested by "sabermetrics?" With an odd number of games, just over .500, by virtue of the odd game, or 16-15. That's not a strong showing, but in the American League West, it would be enough put them only two games behind the Texas Rangers, at 19-14.
And if the A's had gotten as lucky for a few games as they have been unlucky, say, 18-13, they would actually be in first place, a few points ahead of the Rangers. But such luck isn't on the As' side, at least not so far this year.