How is Nick Pivetta’s Curveball Improved this Season?

Nick Pivetta is undefeated in a Red Sox uniform, going 8-0 since joining the Red Sox in 2020. So far this season he has 9.9 K/9, and career low 0.67 HR/9 and 3.40 FIP. One reason for his success may be an improvement he’s made on his curveball.

Pivetta’s curveball has always been a nasty pitch, but slight tweaks in it this season has improved its overall look an effectiveness. For reference here is a look at the curveball from 2019:

Improving the Curveball’s Spin Efficiency

Before we get started, some quick background. Spin rate describes how quickly a baseball rotates about an axis after it’s released. For example, the ball below has backspin and is rotating around the blue line. The spin rate would tell us how many revolutions the ball has around the line per minute.

Nick Pivetta’s spin movement diagram tells us that the spin of his fourseam (shown in red) and curveball (shown in blue) exactly mirror each other on the clock face. This means that they are rotating about the same axis but in exact opposite directions. A lot of pitchers strive for the mirroring spin because it leads to increased deception.

This aligned pitch mirroring was not the case for Pivetta in 2020. While it was pretty similar, the curveball spun more frequently from the 7-8:30 position on the clock vs 6:30-7:30 in 2020.

In addition to the mirrored movement in 2021, the spin efficiency on Pivetta’s curveball is 92%. This is improved by 16% from 2020, when his spin efficiency was 92%.

Spin efficiency is important and more telling than simply looking at the spin rate of a pitch. It describes the percentage of the raw spin rate that directly impacts the pitch’s movement. For fastballs, change-ups and curveballs, the closer the spin efficiency is to 100% efficient the better, and for sliders the ideal range in efficiency is between 0-35%.

In terms of how Pivetta achieved this improved efficiency, I am not sure. There is no noticeable change in release point or delivery. It is possible he tweaked his grip, but hard to tell based on available information.

What kind of movement is Pivetta getting on his curveball as a result of the increased efficiency?

Spin efficiency is directly related to the movement of pitches. Comparing his curveball movement in 2020 to that in 2021, we can see that it is getting more drop.

The curveball is moving an additional 5.4 inches vertically when compared to curveballs of similar pitchers. The run value of the curveball has also improved from 3 runs to 0 runs, which is the average value. For pitchers, the lower the run value per pitch, the better.

What are the Results of His Curveball?

It’s great that Pivetta’s improved the efficiency of this pitch, but it really only matters if it’s getting the desired results.

So far this season, the strike rate on his curveball is up 6.7% and the opponent slugging percentage is down 0.323. The whiff percentage is also down, but only by 2%.

The sample size on the curveball is only the smaller side, due to pitching in 5 games in 2020, compared to 10 games so far this season. Even though the sample is small, this still represents an overall improvement.

How is this improved curveball playing with other pitches?

We can’t just look at Pivetta’s curveball in a vacuum, so let’s see how it’s interacting with his other stuff.

Fourseam

First, let’s start with the pitch it mirrors, the fourseam. Just a reminder that mirroring is good to have because it improves deception of both pitches.

The results against Pivetta’s fourseam are improved across the board when looking at strike rate, whiff rate, and opponent SLG.

Slider

In 2021, Pivetta is actually throwing his slider more than the curveball for the first time in his career. He increased his slider usage by 8% and decreased his curveball usage by 5%. In particular, the slider usage increased significantly first pitch versus both right and left handed hitters.

The slider efficiency is 35%, which falls in the ideal range of 0-35%. It also has above average vertical and horizontal movement compared to those of similar pitchers.

The 86 mph slider represents a midway velocity pitch between the 95 mph fourseam and the 79 mph curveball. The differences in velocity help throw off a hitter’s timing.

All that being said, the results of his slider are down this year. Whiff percentage is down and opponent slugging is up.

We can see how his progresses as he gets more starts throughout the year, but something to keep an eye on.

Concluding Thoughts

Nick Pivetta is taking his curveball took the next level this season. It’s interaction with the fourseam is improving deception and, therefore, the results against both pitches.

The increased use of the slider can be an attempt at breaking up the velocity gap between the fourseam and curveball to make Pivetta’s pitches harder to read.  So far, the results are not reflecting an improvement, but we can keep this in mind as the season progresses.