Second-best run differential belongs to ...

Yes, the Seattle Mariners. After Monday's 12-3 shellacking of the Red Sox, the Mariners have scored 313 runs and allowed 267, good for a run differential of plus-46, well behind Oakland's plus-135 but better than the Nationals and Giants (plus-43) and Angels (plus-42).

Of course, the standings are determined by wins and losses, not run differential and the Mariners' positive total -- despite ranking last in the American League in OBP and wOBA -- could mean several things:

1. The Mariners are a good team.

2. Run differential, at least at this point in the season, is a misleading barometer of a team's strength.

3. The Mariners have underachieved (their expected record, bases on runs scored and allowed would be 45-32 instead of 41-36).

4. The Mariners have overachieved (the offense is still awful).

5. Felix Hernandez is a god if he can carry this team to the playoffs.

Are the Mariners this good? Even though I'm a Mariners fan, it's hard to believe a team with this bad of an offense is a serious playoff contender, but the Mariners are certainly good at run prevention (even though their No. 5 spot in the rotation with Erasmo Ramirez and Brandon Maurer has been a disaster). They've scored more runs than expected (not that they've scored a lot) given their hitting totals because they've raised their average from .241 overall to .266 with runners in scoring position. Robinson Cano and Kyle Seager -- really, the only two solid hitters in the lineup -- have both been terrific with RISP, Cano hitting .368/.473/.614 and Seager .299/.365/.552. But what happens if those two don't keep driving in runs at this clip?

Mariners fans have come to expect the worse after a decade of mostly miserable baseball. For some reason, despite the brilliance of Hernandez and Hisashi Iwakuma and a bullpen that has been outstanding of late (fourth-best ERA in the majors and best since May 1), we keep wondering if this team is a mirage. Is this the high-water mark of the season? When will Fernando Rodney implode? Chris Young can't keep winning games with that strikeout-to-walk ratio, can he? When will the league figure out Roenis Elias? Endy Chavez is batting leadoff!

Of course, saying the Mariners have the second-best run differential ignores the fact if the season ended today, the Mariners are merely tied with the Orioles for the second wild card, with the Royals a half-game back, the Yankees one game back and the Indians and Twins 3.5 games back. In other words, it's still anybody's game. The FanGraphs playoff odds that we use here at ESPN look at what a team has done so for, projected performance the rest of the way and schedule. It sees the odds of making the playoffs like this:

Athletics: 97.1 percent

Tigers: 86.5 percent

Angels: 78.7 percent

Blue Jays: 67.4 percent

Mariners: 37.9 percent

Orioles: 32.2 percent

Royals: 30.1 percent

Yankees: 25.0 percent

Indians: 21.3 percent

Red Sox: 14.7 percent

Hey, 38 percent is far from a sure thing. But it's a whole better than zero.