Arthur: Why did pitchers stop throwing fastballs to the the A’s?

From SABR member Robert Arthur at Baseball Prospectus on October 2, 2014:

My intuition wants me to believe that the A’s collapse was inevitable somehow. It’s frustrating to look at a team like the A’s, made cleverly and on a shoe-string budget by a sabermetric hero, failing for no other reason than six inches of Josh Donaldson‘s positioning and tremendously poor injury luck. Naturally, I want a reason, some scapegoat, or at least a clue, as to why these promising A’s folded so readily.

Whatever the ultimate cause, Oakland’s collapse is primarily on the offense, whose production fell by something like a run and a half in the second half of the season. The Oakland lineup is loaded with potent hitters, and it made no sense for them to fizzle. One can’t predict ball.

I should note here that the offense performed perfectly capably in the wild-card game, putting up eight runs against the excellent combination of James Shields and the KC bullpen (with a special guest appearance by Yordano Ventura). For a night, whatever offensive struggles ailed them were less of a concern than Jon Lester’s inability to throw over to first and Ned Yost’s Retro Small-Ball Attack. Even so, Oakland never would have had to be in the wildcard play-in if their hitters had kept up their performance in the first half, so I’ll focus here on that offense.

There might be a clue to the Oakland breakdown in the approach pitchers used against them as the year went on. Pitch selection is one element of the overall approach, and while different pitchers may possess different repertoires, we can roughly divide all pitches into fastballs and not-fastballs. Generally, players who see fewer fastballs are younger and drive pitches with more authority. Conversely, players who see more fastballs are older and less powerful.

The league average fastball percentage is about 55 percent. For the first three months of the 2014 season, Oakland’s core group of regulars maintained a fastball percentage of 54.1 percent, just a smidge under the average. The group had good power (SLG’s of .412, .421, .383 by month) and plate discipline, and it wasn’t on some fluky BABIP (.298, .265, .301). Everything was going well and in the proper order.

Then, something weird happened. Pitchers started throwing the Oakland A’s many fewer fastballs.

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Originally published: October 2, 2014. Last Updated: October 2, 2014.