Here the A's sit, 24 games over .500 with a full series to play before the All-Star Break. Oakland's 58 wins match its most ever through 92 games. Even crazier is the Athletics' run differential, +147, which is good for an expected (Pythagorean) win-loss record of 63-29. So yes, you could still argue that Oakland is underperforming.
While that might be true, the A's have still blown away the league this year, plain and simple. Their winning clip of .630 makes them the only team in baseball playing at .600 or higher, and Fangraphs is so impressed with them that it pegs their odds of reaching the playoffs at a cool 99.7 percent. There are 70 games left to play.
All this is to say that Oakland should be running away with the American League West. If the Orioles were 58-34, they'd lead the AL East by 10.5 games. The Tigers would lead the Central by 10.5, too. The Nationals would lead the NL East by 8 games, and that division is tied right now. The Brewers' lead would be 7.5 games, and the Dodgers would lead by 8.
But baseball's second-best team is in the AL West, and the Los Angeles Angels aren't going anywhere. Their bullpen isn't the best and their rotation could use a bit more depth, but the Angels have some type of alien/robot thing called a "Mike Trout," and it happens to be the most productive player in baseball this side of Barry Bonds.
The Angels are 54-37, which would put them in first place in any other division in baseball. They have a +80 run differential, second best in baseball. ESPN gives them an 86.5 percent chance of reaching the playoffs, with 71 games left to play. Their Pythagorean record is 54-37. At least they aren't underperforming.
So the A's are playing historically well, yet if things continue the way they're going, all it would take is one bad week for the AL West to slip out of what's currently a firm Oakland grasp.
Oh, and then there are the Mariners.
The Mariners have the third best run differential in the American League, fourth best in baseball, and — poor things — their Pythagorean record is 53-39, though their actual record is a paltry (by AL West standards) 49-43. But the Mariners play in the AL West, and they have the distinct privilege of playing 23 games against baseball's two best teams before reaching the All-Star break.
If the playoffs started tomorrow, the AL West would be guaranteed a representative in the ALCS. The Angels and Mariners would play once for the right to face Oakland in the Division Series, and the winner would face whoever prevailed in the Baltimore-Detroit series.
Seattle is ahead of both second-place teams in the American League, and it doesn't look like the Mariners are going anywhere, either. Both the Angels and Mariners will be buyers at the trade deadline. Seattle would be content with a wild-card spot, while the Angels might as well gun for the division.
So if you treat run differential as the powerfully predictive statistic it is, you realize that Oakland, the Angels, and Seattle are quite possibly the three best teams in baseball. None are without their flaws (the A's have fewer than most, though) and all have a good chance of reaching the postseason.
Of course, it doesn't hurt that the Astros and Rangers are the two worst teams in baseball by run differential. But even those teams can be immensely entertaining. Houston's Jon Singleton is Exhibit A for why the Astros might be the best team in their division by 2017, and Texas' Yu Darvish is still one of the league's best when he's pitching against teams that aren't from Oakland.
This weekend's series between the A's and Mariners is Exhibit A for something else — the ridiculous quality of starting pitching in the division. Tonight's matchup is an incredible one: Felix Hernandez against Jeff Samardzija. Hernandez's ERA is 2.11, while Samardzija's is 2.74, but Seattle will be seeing him for the first time. Bold prediction: not many runs will be scored.
Tomorrow, the A's will send Jesse Chavez to the mound. What an ERA advantage he has — Hisashi Iwakuma's 3.07 pales in comparison to his 3.06. Lather, rinse, and repeat for Sunday, when Chris Young's 3.08 faces off against Sonny Gray's 2.97. So yes, each of the six starters slated to throw this weekend is pitching to a 3.08 ERA or better.
This is a huge series for the Mariners. They're showing as much promise right now as they have at any point in Felix Hernandez's career, and, potentially motivated by the sudden competitiveness, he's turned in his best year yet for them. As the last series before the break, the Mariners have an opportunity to do some damage against the first-place team, making the statement that they're in this thing, too.
Either team could sweep this series, and it'll probably be low scoring. Then again, the A's could rock Felix in the first inning and Seattle could hit Samardzija so hard he forgets how to spell his own last name. Whatever ends up happening, it will be intense and fun, competitive and compelling, just as the last months of play in the AL West will be. It's a three-team race, but we rarely see a three-team race involving teams that are all incredibly deserving of playing October baseball. Then again, all of them probably will.