A lot has been made lately about the horrible state of the Pirates’ defense this year. I touched on the defense being an issue for the Pirates earlier this week, noting that it will probably see some improvements when Josh Harrison and Jordy Mercer return. But even with those two in the lineup, the Pirates have struggled this year defensively.
Another issue for the Pirates lately has been their starting rotation. A lot of their starters have been struggling, including a few of the guys who were doing great in the first half. I started digging around with the numbers, and found that the defense might actually be the problem here as well.
The Pirates have been successful the last few years in large part to their pitching and defense. They’ve added a lot of heavy ground ball pitchers, employed defensive shifts, prioritized catcher defense, and put defense ahead of offense in the infield. This led to some poor offensive results at times (especially with Clint Barmes in the lineup), but a pitching staff consistently playing over their heads
As I noted, the Pirates have had a poor defense this year, due to horrible play from Pedro Alvarez at first base and Neil Walker at second base. Walker ranks 20th out of 22 qualified second basemen in Defensive Runs Saved, and last out of that same group in UZR/150. Alvarez ranks dead last out of 21 qualified first basemen in both categories, and it’s not even close. But what we’ve seen lately has been atrocious. And I believe it’s all due to the loss of Mercer and Harrison.
Both infielders went down around the All-Star break, with Harrison going down before the break, and Mercer going down right after the break. The result since has been that Mercer was replaced by Jung-ho Kang at shortstop, and the Harrison/Kang combo was replaced by Aramis Ramirez at third base.
At shortstop, Kang definitely has the better bat, but Mercer has the better defense. Mercer has a 1.0 UZR/150 this year, while Kang is at -9.0. Those numbers from Mercer match up to last year, when he really made strides to be a solid defender at shortstop. And Kang’s numbers match up with the eye test that shows he can play the position, but can’t be a defensive asset at the position.
Then there’s third base, where Kang profiles much better with a 3.0 UZR/150. Harrison hasn’t been great at the position, but has a -2.3 UZR/150, which isn’t horrible. Both of those are much better than Aramis Ramirez and his -12.5 UZR/150. Once again, this is a number that matches up with the eye test.
When Mercer and Harrison return, it will allow the team to upgrade defensively at shortstop with Mercer over Kang, and upgrade defensively at third base with the combo of Kang and Harrison over Ramirez. And if you’re wondering the potential impact here, let’s take a look at the breakdown of the starting rotation before and after the All-Star break. (NOTE: Stats run through Friday night, and don’t include last night’s start from Charlie Morton).
As I noted, the Pirates lost both Mercer and Harrison around the break. So most of their games before the break were with both players in the lineup, and most since the break have been without both players. The pitching has definitely been down since the break, and it might seem like a coincidence that this came at the same time the defense saw two major blows. But looking at the numbers above, it seems like the defense might be playing a big role here.
The first thing that stands out is the rotation out-performing their advanced metrics in the first half, and under-performing the advanced metrics in the second half. There isn’t much of a difference in the xFIP numbers, but the ERA sees a big drop.
Breaking down the things a pitcher can control, the strikeouts, walks, and home runs all seem to be similar to the first half numbers. The ground ball numbers are down, although I’m guessing that’s probably due to J.A. Happ replacing A.J. Burnett.
The final part is where things really get interesting. The rotation was allowing respectable numbers in the first half, with a .300 BABIP, a 75.4% strand rate, and a 9.2% HR/FB rate. The strand rate is a bit unlucky in the second half, and the home run rate went up a bit, but there’s a massive difference with the BABIP numbers. The Pirates went from a normal .300 BABIP in the first half, to an extreme .371 in the second half.
Now it’s possible that the starting rotation collectively just started having problems and became much easier to hit after the All-Star break. But considering how the strikeouts, walks, and home run numbers are all relatively the same, I find that hard to believe.
What makes more sense is that Harrison and Mercer went down, which led to inferior defensive replacements at their positions, which in turn led to the pitching staff giving up an unlucky amount of hits on balls in play. All you have to do is compare the defensive numbers of Mercer versus Kang at shortstop, and Harrison/Kang versus Ramirez at third base to see how much of a downgrade the team saw with these injuries. And since the rotation really started falling apart right after those injuries, it’s easy to draw a correlation between the injuries and the starting rotation struggles.
I don’t know for sure that the loss of Mercer and Harrison led to a much weaker rotation in the last month. But it wouldn’t surprise me at all if the rotation suddenly finds their first half magic when those two come off the disabled list. The defense will see an upgrade at that time, which will be much better for the pitchers whose problems mostly revolve around allowing an unlucky amount of hits lately.
