You can blame the A's not making the playoffs this year on Bobby Crosby and his tank-like presence in the infield.
Because the A's would've made the playoffs had they had Mark Ellis, according to Baseball Prospectus.
Even then, the A's came within one game of winning it. The root cause, the thing that made the biggest difference, wasn't the weakness of the outfield, which was only sporadically productive, or the absence of Eric Chavez with a broken bone, although that certainly hurt. You have to go back before opening day, when Mark Ellis was lost for the season. PECOTA's 60th-percentile projection for Ellis showed a VORP of 17.4, or 1.7 wins added. Given their weaknesses at other positions, the A's needed Ellis to have a chance to reach this projection or exceed it, as he did in 2002. Instead, they got Marco Scutaro, VORP 12.6. Now add the huge defensive difference between the two players, and you easily surpass the slim margin by which the Angels won the West.
Now, I'm not sure that I necessarily believe that, but it's true that Ellis would've been better defensively that anything the A's threw out there.
Whether that meant two more wins or not, I'm not sure and no one will ever truly know.
But the truth is that the A's wouldn't have gone far in the playoffs with the pitchers struggling the way they were any way.
So, the speculation is just that. A fun way to dissect a team coming up short.