By MARK SIMON

The Athletics were one of the surprise teams in baseball last season, winning the second AL Wild Card and challenging the Astros for the AL West title.

Chances are that you know the Athletics had the best defensive player in baseball last season in third baseman Matt Chapman. But they were also good at something that had almost nothing to do with Chapman.

As you can see in the newly-listed numbers on Fangraphs, Oakland ranked second in MLB with 36 Shift Runs Saved, trailing only the 39 by the Diamondbacks. It’s largely the reason that the Athletics led the AL in overall Defensive Runs Saved.

Those two teams used shifts at dramatically different volumes. The Diamondbacks ranked eighth in the number of shifts they used on balls in play with 1,391. The Athletics ranked 25th, utilizing 883. But the Athletics got great value out of the instances in which they did shift.

So what were the characteristics of the Athletics’ shift that allowed them to be so good despite the minimal usage, relative to the rest of MLB?

Strategic Change

In 2017, the Athletics used full shifts (ones with three infielders on the pull side) and partial shifts (two infielders on each side, but at least two fielders significantly deviating from normal positioning) about the same number of times (170 ground balls and short line drives into full shifts vs. 188 into partials). That’s a recipe for trouble. Full shifts are far more effective than partial shifts at thwarting base hits on grounders and short liners.

Case in point: the Athletics allowed a .182 batting average on those type of batted balls against full shifts that season and a .340 batting average on them in partial shifts.

In 2018, the Athletics changed approaches. They used full shifts more than twice as often as partial shifts. Their success on full shifts continued. Opponents hit .162 against them on their grounders and liners, the second-lowest batting average allowed in MLB. And with greater selectivity on partial shifts, opponents’ batting average came down as well (.257 on grounders and liners).

Sure-handed Middle Infielders

The Athletics did something a little different than most teams and different than they had in 2017, sometimes playing their shortstop, Marcus Semien, in shallow right field when they shifted a left-handed batter. They took second baseman Jed Lowrie out of that spot and moved him to a spot more in line with where a shortstop would play in the shift. Semien is five years younger than Lowrie and can cover more ground. The move worked well for both.

Semien, a much-improved defensive player in 2019 in non-shift situations, was highly valuable in this defensive alignment. Of the A’s 36 Runs Saved from shifts, 7 came from Semien, up from 2 the previous season.

Similarly, the Athletics got 7 Shift Runs Saved on balls in which Lowrie was the primary fielder in a shift, up from -2 on a similar number of balls the previous season.

Unrelated, but worth noting: The Athletics recorded only one run saved on balls hit to Chapman in shifts. This success was mostly about Lowrie and Semien (with a little help from Matt Olson).

When shifting a righty, it almost always worked

The Athletics were infrequent shifters of right-handed hitters, but when they used a shift, it usually did the trick. Righties who hit a ground ball against an A’s shift had a .165 reached-base percentage (how often they reached on hit or error) on 79 ground balls. They reached 13 times when the average hitter would have reached 22.

That’s not a large sample by any means, but it shows how the Athletics helped themselves in the stat by converting these outs.

Outlook

The Athletics’ infield defense returns its two cornerstones in Matt Olson and Chapman at first and third, as well as Semien at shortstop. They’ll break in a new second baseman in Jurickson Profar, whose major league experience at the position consists of a little more than 500 innings. He’ll replace Lowrie, who signed with the Mets this offseason.

The things to watch will be whether Semien maintains his improvement and whether Profar is comfortable in Oakland’s defensive alignments. Also worth keeping an eye on is the Athletics’ shift usage, both in total and in how often they play three infielders on the pull side. They’ll likely need similar success to contend with the Astros again.