At this point in the year, knowing what we know now after four months of the season in the books, I think one could make the argument that Rick Porcello is the key to the rotation. The most popular pick would be David Price (and I am not at all convinced that would be a bad argument), but at this point I think we know what Price is for the most part. He’s been good much more than he’s been bad. Porcello, meanwhile, has been up and down all year, and while he’s pretty much always a good bet to get deep into a game and save the bullpen, you don’t know what the results will be. For two months, he has been great. For the other two months...well, not so much.
If you go month by month, it’s been a one-on, one-off trend for Porcello in 2018. In March and April, he tossed 40 innings with a 2.23 ERA while allowing a .216 wOBA (an offensive statistic on the scale of OBP). Then, he started going down the rollercoaster in May, allowing a 5.35 ERA with a .356 wOBA. The rollercoaster started on their way back up with a 3.48 ERA and a .291 wOBA. Finally, in July, the ERA went up to 5.74 ERA in July while his wOBA climbed to .373. What’s particularly interesting about all of this because his peripherals have remained mostly consistent through the year. His strikeout rate has stayed between 22 percent and 24 percent in every month this year, and besides March/April his walk rate has hung around 6-7 percent this year.
Ultimately, the biggest difference has been batting average on balls in play. By month, here are the BABIPs Porcello has allowed this year: .259, .343, .250, .363. That’s a pretty big difference, and since we’re talking about individual samples spanning between 25 innings and 40 innings, there’s a lot of noise here. BABIP is inherently known as a luck stat, which would mean that his luck has fluctuated all year. Of course, things aren’t always that simple. Has Porcello been making his own luck, and is there something to watch for to figure out which way he’ll trend next?
The first logical place to start here is with batted ball data. Porcello’s entire Red Sox career has been trying to find the right balance between his old groundball-style from Detroit and his newer strikeout/flyball profile. When the righty is at his best, he’s striking out between seven and eight batters per nine innings with a ground ball rate between 45 and 50 percent. That is where he lived in 2016 when he won the Cy Young, but last year he took things too far when his groundball rate fell to 40 percent and it resulted in a massively disappointing season. His groundball rate has fluctuated a bit this year, but there’s no real correlation between his success and his keeping the ball on the ground. He has two months with a 49 percent groundball rate and two with a 40 percent rate, but one of each were good and one of each were bad months. Even looking at quality of contact and other batted ball metrics, there is really no correlation to be found between his good and bad periods of the year.
The next thing to look at with Porcello would be his pitch usage, as this has also been a balance he’s been trying to strike as a member of the Red Sox. This goes hand-in-hand with the groundball theory, as he’s trying to find the right balance between his two-seam and his four-seam fastball. Here, we do have some correlation. The two lowest periods of two-seam usage have, somewhat unsurprisingly, come in his worst months. His four-seam usage hasn’t necessarily increased during these times, but when Porcello has been at his worst he is only throwing his sinker about a quarter of the time, rather than a third of the time when he’s going well. While he’s been in Boston, Porcello has always fallen into traps where he searches for strikeouts with high four-seam fastballs. It does work at times, but inevitably it eventually leads to hard contact.
The final portion of this is how often Porcello is hitting the strike zone. The righty has always been someone who pounds the zone and avoids free passes, but at times he can get into trouble when he’s hitting the zone too much. Hitters know strikes are coming, and they are ready to jump early in the count and take advantage of predictability. As it turns out, Porcello has hit the zone more often in the bad months than the good ones, though it’s not a massive difference. You can look at his trends with hitting the zone here. This can also be a little misleading, to be fair, because this counts all pitches in the zone the same. Porcello is obviously at his best when he’s at the edges of the zone, and if he’s hitting those spots a lot it won’t be a problem. It’s when he catches too much plate that he starts to become very hittable. His stuff just isn’t good enough to get away with those mistakes.
The Red Sox could really use a hot Porcello as they get closer to the postseason, but the way this season is going you never really know which version you will get. Of course, like I said above, the righty is pretty much always good for a deep outing, and there’s plenty of value in that in and of itself. If he wants to take things to the next level, though, look for his sinker usage and his ability to avoid the middle of the strike zone. If he’s dotting the corners with that two-seamer, things are going to go extremely well. The good news is that he’s coming off perhaps his best start of the year, so hopefully he can ride that momentum into Thursday’s start, and beyond.