Jake Arrieta will again pitch against the Pittsburgh Pirates on Friday. In his regular-season career (thus not counting his shutout against them in the 2015 National League wild-card game), he has a 1.58 ERA in 11 starts against the Pirates.

Best ERA vs. One Team Active Pitchers (min. 10 starts) Opponent Clayton Kershaw 1.29 Mets Adam Wainwright 1.48 Astros Jake Arrieta 1.58 Pirates * Source: Elias Sports Bureau

The Elias Sports Bureau notes that only two active pitchers have made at least 10 starts against a team with a lower ERA, as noted in the chart on the right.

The Chicago Cubs are 8-1 in Arrieta's starts against the Pirates, with the loss coming via shutout.

In other words, when the Cubs have scored a run against the Pirates in a start by Arrieta, they have won.

Taking out the time in Baltimore ...

For the purposes of this exercise, we’ll ignore the two starts Arrieta made against the Pirates while he was with the Orioles, as he was a much different pitcher in those days.

Excluding those starts, which limits the time frame to the Cubs era of Arrieta’s career, regular-season ERA against the Pirates is even lower, 1.31.

So why can’t the Pirates hit him?

Like a lot of things in baseball, it relates to the fastball.

Jake Arrieta Opponents against Jake Arrieta's fastball in hitter's counts (Since 2013) Pirates Other

teams In-zone pct.* 65% 58% Swing pct. 41% 46% Miss pct. 20% 14% *Pct of Arrieta's fastballs thrown in strike zone

Compared with other teams, the Pirates have shown little ability to hit Arrieta’s fastball. Their contact ability, power and patience against the pitch are lacking when juxtaposed with other teams Arrieta has faced since he joined the Cubs.

One difference for the Pirates against him compared with other teams is that they aren’t as aggressive against the pitch. Since Arrieta joined the Cubs, the Pirates have swung at 36.4 percent of his fastballs compared with 41.7 percent for the rest of major league teams.

This hurts the Pirates in hitter’s counts. Arrieta has been more aggressive in those counts with his fastball against the Pirates than he has been against other teams, and the Pirates tend to maintain a relatively passive approach in those situations.

Instead, they attack his secondary stuff

Whereas the Pirates like to watch as Arrieta throws his fastball, they tend to be more aggressive against his secondary pitches (slider, curveball and changeup).

Compared with when they see fastballs from Arrieta, the Pirates swing more, miss more and chase significantly more against his secondary offerings. The same is true when comparing how often the Pirates do those things relative to other teams.

The best word to sum up this strategy for the Pirates: bold.

Since he joined the Cubs, Arrieta’s secondary pitches have been his calling card. In that time, only two pitchers to make at least 50 starts have held opponents to a lower batting average against non-fastballs: Clayton Kershaw and Jose Fernandez.

What this means for Friday…

Arrieta's Fastball Percentage of fastballs Jake Arrieta has thrown in his last four starts June 11 Braves 79%* June 5 Diamondbacks 67% May 31 Dodgers 70% May 25 Cardinals 71% *Career high in a start

Waiting on Arrieta’s fastball and trying to attack his breaking pitches is an especially poor strategy, given how Arrieta has pitched of late.

Arrieta has increased his fastball usage lately, throwing an average of 71.7 percent fastballs in his last four starts.

Three of Arrieta’s four starts with a fastball usage rate of at least 70 percent have come in his last four starts.

If this trend from Arrieta continues, the Pirates’ past strategy against him could lead to the same result: plenty of outs and few (if any) runs.

The Pirates will probably want to attack early and hope that Arrieta’s command isn’t sharp. If they let him get early strikes with his fastball, he’s bound to break out his secondary offerings, which plays right into his hands.