Mets starting pitcher Jacob deGrom uses his slider too much

The 2014 Rookie of the Year liked to use his weakest pitch in the highest-leverage situations. Perhaps he should change his approach.

In case you missed it, Jacob deGrom made his major league debut last year. While he arrived a bit late to the party, it didn't take him long to become the Mets' new sensation and a force to be reckoned with by the league.

deGrom was elected the 2014 National League Rookie of the Year despite pitching only 22 games and 140.1 innings, on the strength of a 3.0 fWAR, a 2.67 FIP, 0.45 HR/9, and a 25.5 strikeout percentage. In his promising first season, the righty showcased a "power arsenal" (Baseball Prospectus) featuring a solid fastball and a hard slider.

Given that some projection systems (such as Steamer and ZiPS) feel that deGrom will regress in 2015, let's dive deeper into his numbers from last year. Specifically, let's examine how deGrom fared in tough spots with runners on base, to see if and how he can replicate the success he enjoyed in 2014.

Here are deGrom's performances in three different scenarios, compared to league-average production.

In 2014, deGrom was better than the league average in all three categories: with nobody on base, with men on base, and with runners in scoring position. This is not really a surprise. However, while he managed to maintain a low walk rate in each situation, his 22.5% strikeout rate with runners in scoring position was quite a bit lower than his 26.8% rate with nobody on. So, the question is, could he have done better?

The obvious answer is yes; everybody can always improve. The interesting part is how. According to Brooks Baseball, deGrom's fastball was his go-to pitch when runners were not in scoring position.

Again, not very surprising, considering how good deGrom's fastball is. However, with runners in scoring position, deGrom appeared to have shuffled his pitches a bit more.

In these scenarios, deGrom used his slider quite a bit more. While his fastball was still his number-one pitch, the slider was clearly his number-two. And so, given that there is a correlation between his increased slider usage and his weaker performance, we want to find out if there is causation.

Using Baseball Savant PITCHf/x data, let's look at batter outcomes with runners in scoring position against each of deGrom's pitches (fastball, slider, changeup/curve):

According to the slider chart, deGrom's slider produced a favorable outcome for the hitter fifty-eight percent of the time. Although he did not concede hits at a higher rate with his slider, deGrom's slider command (40.2% resulted in balls) was clearly an issue.

If we look at deGrom's slider heat map in RISP situations, we'll see that he struggled to keep the pitch in the zone, or even close to it.

Therefore, the drop in deGrom's strikeout rate with runners in scoring positions might have been the result of his poor slider command. Considering the high velocity of his slider (86.8 mph on average, tied for 15th in the majors), we can understand why he liked to use it. However, there might a different solution available to him.

Fangraphs' Pitch Values offer another way of measuring pitch effectiveness. Here are deGrom's 2014 pitch values and how they compared to the rest of the league's:

*minimum 140 innings pitched

As you can see, Pitch Values ranks deGrom's slider as by far the worst pitch of his arsenal. While his curveball and changeup are not as effective as his elite fastball, they are still better than his slider.

If deGrom wants to throw his hard slider as often as he does, he will probably have to be more consistent with it and throw it closer to the zone. Or, alternatively, perhaps he should turn to his other off-speed pitches when pitching with runners in scoring position. While it will be hard to replicate the success he enjoyed in 2014, this change in approach in high-leverage situations could be one way to improve his game.