During the offseason, the Angels signed right-handed pitcher Trevor Cahill to a one-year contract. The Angels were in serious need of starting pitching depth, and Cahill’s extreme ground-ball tendencies appeared to be an ideal fit for the team’s steady infield defense.

However, Cahill has struggled tremendously with the Angels. By earned run average (6.92), only one starting pitcher has been worse than Cahill this year (minimum 50 innings pitched). By fielding independent pitching (6.61) and Wins Above Replacement (-0.6), none have been worse.

Cahill’s rocky 2019 is especially confounding given the fact that the 31-year-old is coming off one of the finest seasons of his career; last year, he posted a 3.76 ERA, a 22.2% strikeout rate, and 2.0 WAR, all of which are among his career bests. This dramatic regression can be traced to the fact that Cahill has not been the ground-ball specialist the Angels thought they were getting. Instead, for the first time in his career, Cahill has been the opposite.

From 2010-2018, 73 starting pitchers threw at least 1,000 innings. Just two, Dallas Keuchel and Tim Hudson, sported lower-ground-ball rates than Cahill’s 56.2%. Not coincidentally, Cahill also allowed home runs at the eighth-lowest rate in that group.

In 2019, though, Cahill has done a complete about-face in both areas. This year, Cahill’s ground-ball rate is down to 40.6%, which is slightly worse than the average starter, and his home-run rate is the worst among starting pitchers. For further perspective, Cahill has induced about two grounders for every fly ball in his career. In 2019, he has permitted slightly more than one grounder for every fly ball. Moreover, he has surrendered 14 home runs in 49 innings this year. In 2018, he allowed just eight homers in 110 frames.

Simply put, Cahill has been hit extremely hard this year; his 45.5% hard-hit rate is worse than 90% of pitchers. This is exasperated by the fact that his strikeout rate is down precipitously, to 17.8%, his lowest since 2013 and far below the league average of over 22%. So, opposing batters are making more contact against Cahill, and that contact is more damaging. That seems like a simple enough explanation for Cahill’s sharp decline, but the question now becomes: Why?

Pitch Selection

To determine the factors responsible for this, we can first look at how his pitch selection has changed since last year. In 2018, Cahill threw his primary ground-ball-inducing pitch, his sinker, 38% of the time. In 2019, however, he has dropped his sinker usage nearly 12 percentage points, with it now making up just over a quarter of his pitches.

The missing sinkers have been replaced by more curveballs and four-seam fastballs. While Cahill threw his curve 15.7% of the time last year, he is throwing it almost 25% of the time this year. And whereas he tossed his four-seamer only a handful of times in 2018, it has made up about one out of every 10 of his pitches in 2019. Cahill has also decreased his changeup (from 24.6% to 22.2%) and cutter usage (from 18.7% to 15%) slightly this year.

Pitch Effectiveness

The increased number of curves is for good reason—it’s Cahill’s best pitch. In 2018, opposing batters hit a measly .145 against the pitch and whiffed on about 35% of their swings at it. This year, opposing batters are having a much easier time putting Cahill’s curve in play—their whiff rate against the pitch is just over 20%—but they have still been mostly unsuccessful against it, as they have hit just .163 with three extra-base hits versus the pitch.

Additionally, despite the lowered swing-and-miss rate, it has still been as effective a putaway pitch as it was in 2018, with nearly a fifth of Cahill’s two-strike curves resulting in a strikeout both this season and last.

Cahill’s other pitches have not fared as well as his curve. For example, his changeup has seen a severe drop in effectiveness. In 2018, he gave up just eight extra-base hits against the offspeed pitch and generated a swing and miss on 38.6% of opponent swings. This year, he has already permitted six extra-base hits against his changeup, and it is resulting in a whiff on fewer than a quarter of swings.

Furthermore, Cahill’s changeup has been a major reason why he is allowing so many fewer grounders now; his changeup’s ground-ball rate is down from 56.6% in 2018 to just 32.4% in 2019, and the average launch angle versus the pitch is up from just five degrees to 17. This change simply comes down to location. As the charts below show, Cahill is having a much more difficult time burying the pitch low in the strike zone.

cahillchusage

Cahill’s changeup location. Source: Baseball Savant.

Last year, 28% of Cahill’s changeups were located in the bottom third of the zone. This year, just 20.6% of his changeups have been placed there. Cahill has also left 22.1% of his changeups in the middle third of the zone this season, while he only did that 14.1% of the time in 2018. For context, the league is slugging .579 on middle-third changeups this season and just .418 on lower-third changeups. That’s the difference between Kris Bryant and Ji-Man Choi.

Unfortunately for Cahill, his problems have not been limited to his changeup. For instance, his four-seam fastball and cutter have both been roughed up to the tune of a .542 slugging percentage. But it has been Cahill’s go-to sinker that has been most responsible for his 2019 struggles; he has permitted six home runs and an astronomical .750 expected slugging percentage against the pitch. For comparison, in 2018, he allowed just two home runs and a .439 expected slugging percentage versus his sinker.

With those numbers in mind, it is somewhat surprising to know that Cahill is inducing grounders with his sinker at about the same rate this year as last year (55.6% vs. 56.3%). However, while opposing batters are not elevating Cahill’s sinker significantly more often, they are doing much more damage to it when they do.

In 2018, opposing batters batters accumulated a 94.3-mph average exit velocity when putting Cahill’s sinker in the air (line drives and fly balls). In 2019, that number is 102.3 mph. Thus, Cahill’s sinker is resulting in many more extra-base hits.

The reasons for this seem quite clear. For one, Cahill is throwing his sinker in the strike zone considerably more often in 2019 than he did in 2018; 59.4% of his sinkers have ended up in the zone this season, compared to just 47.7% last season. In addition, Cahill’s average sinker velocity is at a three-year low of 91 mph, nearly a full mph lower than last year. So, with poor location and diminished velocity, Cahill is providing opposing batters with more opportunities to punish an easier-to-hit pitch.

Conclusion

The Angels have not gotten what they were expecting from Cahill. A pitcher who was best known for his reliably average production coming into this year has been one of 2019’s least effective pitchers. Worse yet, results aside, he’s been the opposite sort of pitcher that the Angels were anticipating—a fly-ball connoisseur instead of a ground-ball master.

Cahill’s issues mainly stem from decreased velocity and an inability to locate his pitches well. Luckily for Cahill, he has benefited from a slight uptick in velocity over his last few starts. If he is to turn his season around, though, he will need that to continue, and he will need to execute his pitches better. As they presently own the third-worst starting rotation in the majors, the Angels will surely be hoping their free-agent investment will be able to do just that.


Featured image via Keith Allison/Flickr.

Posted by Chad Stewart

Twitter: @Chad13Stewart Instagram: @theangelsavenue

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