The Oakland A’s had a nightmarish season in 2015. They had the biggest difference in Base Runs vs. actual record out of any team since 2002. Their bullpen had historically-bad timing. And, finally, their defensive issues were on display most of the year, especially in the early stages of the season when they were on pace for a record-breaking number of errors. The infield was mostly to blame for the last problem, with Brett Lawrie and Marcus Semien routinely exhibiting the sort of lapses that have mostly been excised from players by the time they make it to the majors. It was ugly, and it was a part of why the A’s buried themselves in a hole in the AL West standings before the season was even a third of the way through.

Through May 21st of 2015, the A’s were on pace 169 errors, which would have been the most since the year 2000 by a fairly wide margin. Here’s a graphic from the previously-linked post from May 22nd of last season that shows the error gulf we were witnessing:

The A’s finished with only 126 errors, missing out on a particularly ignominious title. However, much of the defensive blame fell squarely on Semien during the early parts of the season, and for good reason: at the time of the May post, he had accounted for 16 of Oakland’s fielding and throwing errors. By the end of May, some were claiming that the A’s might not be able to afford to keep his glove at shortstop, despite his strong production at the plate. But the team did something about it: they hired Ron Washington to tutor the young shortstop on defense, and he started doing so on May 22nd. They got right to work, with Semien doing throwing mechanics drills, and often fielding ground balls with a plank-like glove to soften his hands:

His pregame fielding routine begins by taking grounders with a “flat glove.” Rather than a soft pocket, it has a flat surface, which forces a player to field the ball with soft hands. Semien fields balls to his left, then his right with the flat glove. Only after that does he slip on his regular glove.

By the modest forms of measurements we have available, the mentoring seemed to pay off, at least on the surface: Semien made “only” 19 errors from May 22nd until the end of the year, improved his fielding percentage by .50 points from what it was before May 21st, and finished the year with positive DRS (+4). UZR/150 really disliked him, but we can attribute that mainly to Semien having the worst Error Runs (ErrR) component of UZR among shortstops in the past 15 years (-12.5).

The standard caveats apply related to this sample size of defensive statistics: they’re hard to trust year-to-year, and we should regress them heavily. The bottom line: Semien had a brutal defensive campaign, but it did get a little better once Washington came on to help. Satisfied that the 24-year-old shortstop was at least on the right track, the A’s made Washington their new third base coach on August 24th, and Semien’s daily dose of fielding drills were scaled back.

There’s another layer to this story, of course, and it was what else happened during the timeframe when Washington and Semien were focusing on his defense. I first stumbled across this interesting factoid during my perusal of a certain popular social media platform, when Joseph DeClercq — a contributor to Athletics Nation – pointed out Semien’s offensive production before, during, and after directly working with Washington. Take a look:

Marcus Semien Offensive Stats, 2015 BB% K% ISO BABIP wOBA wRC+ Pre 5/22 6.1% 21.0% .183 .360 .358 130 5/22-8/24* 6.2% 22.5% .100 .277 .260 63 Post 8/24 9.9% 22.1% .205 .325 .359 131 SOURCE: FanGraphs *Period when Semien was intensively working on defense with Ron Washington

The numbers are almost comically similar before and after working with Wash on defense, and it’s easy to see what happened during their time together: Semien couldn’t hit a thing. He was the second-best offensive shortstop in the majors by wRC+ from Opening Day to mid-May; then, from May 22nd to August 24th, he was Jean Segura. After August 24th, he went back to posting a similar wRC+ to Ryan Braun.

Small sample size abounds. BABIP happened a little bit. But so did ISO, and so did walk rate, which stabilize more quickly than other offensive stats. There’s signal in the noise, and there are brief bookends of outstanding production here. Let’s do this – have a look at Semien’s plate discipline statistics, again dividing them into our three time frames:

Marcus Semien Plate Discipline, 2015 O-Swing% Z-Swing% Swing% O-Contact% Z-Contact% Contact% SwStr% Pre 5/22 25.3% 59.6% 41.8% 64.1% 88.6% 81.0% 7.8% 5/22-8/24* 28.5% 67.0% 48.0% 54.8% 88.2% 78.5% 10.1% Post 8/24 22.2% 61.1% 40.3% 62.9% 86.6% 79.6% 8.1% SOURCE: FanGraphs *Period when Semien was intensively working on defense with Ron Washington

Semien was simply more aggressive for the roughly three months he was working on his defense, and his out of zone contact/swing rates tell the story of his offensive struggles during that period. He also saw a larger majority of first-pitch strikes during the three middle months, which certainly could’ve been a contributing factor to his increased aggressiveness — as with most situations in baseball, nothing stands alone. I am reminded of the John Muir quote: “When we try to pick out anything by itself, we find it hitched to everything else in the Universe.” Despite not knowing the man, I confidently state that Muir quite possibly may have been talking about our nation’s pastime.

The point being: Marcus Semien was really good at the plate for almost two months. Then, because of his history as a utility player, he actually had to learn how to play shortstop full time, and his offense suffered. Once his tutelage was over, he was an incredibly similar version of who he was at the plate before his defensive lessons. That’s not the entire story, of course. These things are never that simple — John Muir tells us so. But it makes a lot of sense given the knowledge that shortstop is an incredibly hard position to play defensively. Learning the basics almost from scratch while trying to effectively hit major league pitching at the same time is a monumental task. A human being can only do so much at one time, even ones that are gifted enough to go to Cal Berkeley and then play in the big leagues. Semien has shown signs that he really can hit. Now he should have the basics of playing shortstop down. At such a thin position, that seems like an interesting — and potentially very valuable — place to be.