Drew Pomeranz’s home run issues

I’ve spent a lot of time this offseason discussing the rotation, because it’s such an interesting part of this club for 2017. It’s likely the portion of the roster that needs the least amount of work, but that doesn’t mean it’s a sure thing. There are a lot of variables with this unit, and Drew Pomeranz sort of embodies that. He will probably find himself directly in the middle of the group, bridging between the should-be sure things in David Price and Rick Porcello and the unknowns represented by Eduardo Rodriguez and the Steven Wright/Clay Buchholz duo. Based on his history, one could reasonably expect him to join either half of the rotation.

If we look at Pomeranz’s 2016 campaign, it was really a tale of two seasons. Obviously, the now-28-year-old (Happy Birthday, Drew) didn’t spend the whole year in Boston, with 17 of his 31 appearances coming in San Diego. For that span of the season, he was phenomenal. The former first-round pick pitched to a 2.47 ERA with over 10 strikeouts per nine innings while inducing ground balls on over 50 percent of balls in play. He was one of the best pitchers in the National League and earned an All-Star bid for his efforts. Back when the trade actually happened in mid-July, I wrote that his breakout season with the Padres included some tangible changes to allow it to happen.

After coming over to the Red Sox, it would be unfair to say the second act of Pomeranz’s season was terrible. Still, it was certainly disappointing after what he did on the left coast. While he showed off some real flashes of the talent he possesses, particularly when you consider he was experiencing the largest workload of his career, and there are plenty of reasons for optimism, the numbers weren’t great. DRA, which is my favorite pitching stat out there, believes he was just as good in Boston as we was in San Diego, but it’s hard to deny his 4.59 ERA and his 4.78 FIP. The overarching issue that plagued Pomeranz’s time with Boston, of course, was the long ball.

Before the trade, the lefty allowed just 0.7 home runs per nine innings, which was well below the league-average starter’s rate of 1.2. After the deal, however, that number jumped way up to 1.8. In fact, of the 14 appearances after the trade, Pomeranz managed to keep the ball in the yard just twice, and one of those instances came in a 1.1-inning relief appearance. In 92 percent of his starts it was a major problem for him, and there are a few noticeable reasons for the trend.

Clearly, there are a couple more obvious reasons behind the spike in the long ball. First of all, he was moving from the National League to the American League. It goes without saying that the league with the designated hitter is going to be more difficult to face as a pitcher and will feature more potent bats on average. Additionally, he was moving from the friendly confines of Petco Park (not to mention Dodger Stadium and AT&T Park in his division) to the hitter-friendly Fenway Park along with the other bandboxes in the AL East. These two factors, along with a little bad luck, could be enough to explain the entire explosion. That explanation leaves me unsatisfied, though, and suggests we should expect the same going forward. However, there are other trends to look at.

The first lies with his pitch usage, which is something I talked about a lot in the piece I linked above. As I mentioned there, a big reason for Pomeranz’s jump forward was the development of a third pitch (the cutter) to get away from his fastball and set up his nasty curveball more. After joining the Red Sox, he still utilized his secondaries, but not as much. As a result, he was throwing his fastball over 42 percent of the time compared to 36 percent in his time with San Diego. We know that fastballs are the easiest pitch to hit out. This coincided with a lower ground ball rate on the pitch and a higher home run to fly ball ratio. The latter can be blamed on the move to the AL and the East’s ballparks, as it wasn’t a huge jump, but the former and the overall number of homers on the pitch is thanks to being able to expect seeing it more often.

It wasn’t just the fastball he struggled with, though. The cutter went from being a weapon in San Diego to a problem in Boston. While he threw the pitch at roughly the same rate, he allowed far more extra base hits and increased his home run rate on the pitch threefold. Part of that is more familiarity with the offering. Pomeranz really just started using the pitch in 2016 and by the time he got the Boston there were more scouting reports available. It wasn’t just that, though. Look at the zone profiles for his cutter from San Diego compared to Boston.

The left image is from his time with the Padres, while the right is with the Red Sox. It’s abundantly clear that he had a harder time moving off the plate after the trade. Prior to the deal, he was pounding the glove side of the plate, putting the ball away from lefties and in on the hands of righties. After coming to Boston, whether because of fatigue or something else, the pitch was left over the heart of the plate far too often.

Pomeranz may very well be the difference between this being a good rotation and a great one, and they’ll need consistency from the lefty to be the latter. That, in turn, means he’ll need to avoid allowing so many home runs. Part of it is unavoidable, with his change of leagues and parks. Part of it is likely due to his increased workload, which is an adjustment he should make moving forward. Another part, though, is the ineffectiveness of his new cutter and the predictability of his fastball. Pomeranz has the pitch mix to make everything work, as we saw with the Padres, but he’ll need to utilize it better if he can be consistently good over a full season.