The Mets’ rotation was merely decent in the first half of the 2019 season

When the season got to the All-Star break, Mets starting pitchers were right at the middle of the pack in Major League Baseball. Their collective 4.45 ERA ranked 15th out of 30 teams. Before the season began, Allison McCague’s season preview of the Mets’ starting rotation addressed the legitimate concerns about the rotation. On top of that, there were some unexpected circumstances that are vitally important to understanding the rotation’s performance.

The baseball being used by MLB this year is wholly different than the one last year. As Dr. Meredith Wills has documented, the ball has changed in terms of aerodynamics and spin. Pitchers who throw harder sliders have seen an under-performance of their pitches relative to expected production.

At the break, the Mets had six of the top 25 sliders in baseball in terms of average velocity. Four of those sliders belong to starters: Steven Matz, Noah Syndergaard, Zack Wheeler, and Jacob deGrom. In addition to the baseball, Mets starters were pushed deeper into starts than they had been in the past. All of that helps put the the rotation’s performance into context.

deGrom’s slider is not as dominant as it was last year, but he had a 3.27 ERA at the break, which was still good for 17th-best in baseball. Like the rest of the league, his HR/FB ratio has jumped—by 8 percentage points in his case. Having signed a contract extension before the season, deGrom is certainly delivering on his end of the deal. He has looked terrific in many of his starts, and while he might not be having a Cy Young type of year so far, he is still one of the best pitchers in the game.

The Mets expected great things from Noah Syndergaard. He was good, if not great, in 2018 despite missing some time with injury and illness. This season has been another thing. Syndergaard had a mediocre first half, with a 4.68 ERA, despite flashing brilliance in some of his starts. His slider is not nearly as dynamic as it was in 2018, jumping from a .455 OPS against to .926 OPS against despite having 2 miles per hour less in average exit velocity. With his slider being more hittable, he has dropped his usage of it from his normal 20% of the time last year to about 10% in 2019. Syndergaard’s success in 2018 stemmed from the execution and dominance of his slider, so without arguably his most effective pitch, he appears to be struggling to readjust.

Steven Matz’s 2018 was a big step for the injury-prone pitcher, as he was finally was able to prove that he could pitch a full season. Yet in 2019, he’s struggled, and he has had a 4.89 ERA at the break and had given up 18 home runs in only 81 innings of work. His slider and fastball have been extremely hittable—for a .514 SLG and .510 SLG, respectively.

One of the few nice stories in the starting rotation in the first half was Jason Vargas, at least in terms of his on-field performance. Despite throwing a fastball that’s around 88 miles per hour on average, he’s had some success. He was second only to deGrom in the rotation in terms of ERA at the break. Off the field, Vargas was a different story.

Zack Wheeler’s arsenal and usage look roughly the same as last year, with a slight bump in his usage of the changeup, but he had a 4.69 ERA and 3.66 FIP at the break. He just does not seem to be missing bats at the same rate he did last year, with an almost 5% dip in whiff percentage from both his curveball and splitter. The Mets sacrificing of defense at multiple positions might be playing a part in his inflated ERA, and before he could make his first start of the second half, he hit the injured list with shoulder fatigue.

Despite having gotten the vast majority of their starts from the five pitchers who were in the rotation to begin the season, the Mets just didn’t get much in the way of production in the first half.