No one expected the Cubs to be good this year; no one's really expected the Cubs to be good in almost a decade. Still, they've managed to underperform even their low, unreconstructed expectations. At 12 games under .500, only the Tampa Bay Rays have a lower win percentage—and given that the Rays play in the challenging AL East, you could make a case that the Cubs are the worst team in baseball.

It wasn't supposed to be this way. Last year the Cubs were the third-worst team in baseball, at 67-95, three games better than the blown-up Marlins and 12 games better than the rebuilding Astros. And that was a year in which their two best players, Anthony Rizzo and Starlin Castro, completely collapsed. Here's a look at their batting average / on-base percentage / and slugging percentages:

• Rizzo slashed .285/.342/.463 in 2012, fell to .233/.323/.419 last year—with a .258 average on balls in play, eighth worst in baseball—and is back to .269/.402/.461 in 2014.
• Castro was one of the worst regulars in baseball last year, hitting .245/.284(!!!)/.347 last year; he's back up near his 2012 numbers this year.
• Jeff Samardzija, their best young pitcher, also struggled—his ERA increased from a promising 3.81 to a mediocre-to-bad 4.34. This year he's been excellent, with a 2.54 ERA, good for seventh in the National League.

And yet Samardzija is 1-5 this year, and the Cubs are in the running for the worst team in the league. What's gone wrong this year? Remarkably enough—or not so remarkably, given the team—they've been remarkably unlucky for the third year in a row.

The Cubs' average run differential this year is -0.3; in other words, in an average game, they'd lose by one-third of a run. The worst figure in the league is -0.9, shared by the Diamondbacks and Phillies, who have win percentages of .410 and .421, respectively. The Cubs are tied with Minnesota (.491) and the Royals (.475), neither of which are good teams, but they're both outperforming the Cubs and within a stone's throw of .500.

Baseball Reference calculates that the Cubs "should" have four more wins than they do, making them the second-unluckiest team in baseball. (The As, with a .627 winning percentage, have lost five more games than their performance suggests.) Baseball Prospectus has them underperforming by six games, again second-worst in baseball, just behind the Rays at seven games.

Which is exactly what happened last year. Baseball Reference has them losing five games to luck in 2013, as well as four in 2012, both near the worst in baseball.

Paralleling that failure has been the Cubs' clutch performance. Fangraphs has a simple formula for this, essentially measuring a player's performance in high-leverage situations. And in the past couple years, the Cubs have choked across the board.

The result is that the Cubs had the worst record in one-run games in 2012 (15-27; the luckiest team, Baltimore, went 29-9); the second-worst in 2013 (18-36); and the fourth-worst in 2014 (5-10). 

In a one-run game, luck and/or clutch performance makes the difference, and the Cubs have been getting killed in those situations.

And that's… unusual. It shouldn't matter, at least not too much, whether the Cubs were a good or bad team those years. The "clutch" number is supposed to be relative to overall performance:

No matter how important the media makes clutch performance out to be, it does not refer to performing well with the game on the line. Instead, it refers to performing well in these types of situations relative to all others. The statistic can be summed up by the question, “Does the player raise his game in important situations?” If not, he is not clutch, no matter how great his numbers are in high leverage plate appearances.

So, in theory at least, the Cubs have been a bad team that has played worse than their badness in high-leverage situations, and they're on their third straight year of that, for both pitching and hitting.

As far as I'm aware, there's no evidence that teams consistently over- or underperform their clutchiness, though there's evidence that it's a measurable skill for players. They're a bad team, but not the worst. Someday soon, their luck should change—not the Curse, perhaps, but enough for a more comfortable mediocrity.