Analyzing Whitlock’s Arsenal

How can Garrett Whitlock return to his 2021 form?

When you hear the name Garrett Whitlock, you probably think you are in for another debate of whether or not Whitlock should be a starter or reliever heading into 2024. I am going to spare you from that debate as there will be plenty of time in the future to revisit that conversation. I was on Baseball Savant’s website and noticed 2 significant differences in Whitlock’s arsenal from his dominant form in 2021 and his 5.15 ERA in 2023.

Before we talk about the arsenal differences, THE obvious difference from 2021 to 2023 is that Whitlock was used as a reliever in 2021. Almost every single pitcher sees their stuff play up when they only need to throw an inning or two. Whitlock’s velocity was much better as a reliever compared to when he was starting over the last 2 seasons. The uptick in velocity could simply be the reason why Whitlock’s numbers have dropped off. The Sox right-hander has also dealt with injuries over the last couple of seasons and maybe he has been pitching when he isn’t 100%. But I do think it is worth investigating the change in his arsenal and questioning if that has anything to do with his inconsistencies over the last 2 seasons. 

Where did the 4-Seam Fastball go?

If you look back to when Whitlock had a 1.96 ERA in 2021, he was throwing his 4-seam fastball 9.5% of the time. Back in ‘21, the 4-seam fastball was not one of his most used pitches but it was a pitch in which he was able to put hitters away 31% of the time, which was the highest percentage of all of his pitches. If you fast forward to last season, Whitlock threw his 4-seam fastball only 8 times all season, or 0.7% of the time. Whitlock practically eliminated this pitch from his arsenal last season. This decision is super interesting because if you look back to Whitlock’s ‘21 numbers on the 4-seam fastball, opposing hitters hit .061 off of his 4–seam fastball. Why you would decide to eliminate that pitch is completely head scratching to me. 

The elimination of the 4-seam fastball seems counterproductive in today’s game. The plan of attack from the majority of pitchers is to throw fastballs with high velocity above the zone to get hitters to chase. Whitlock’s 4-seamer was that pitch back in 2021. Last season, Whitlock’s only pitch to attack hitters above the zone was his sinker, which historically has not been a pitch pitchers use up in the zone. Whitlock did not get the desired results with the sinker as he only put batters away with the pitch on 12.8% of the time, a significant drop off from his 31% with the 4-seam fastball back in 2021. 

I understand Whitlock’s velocity was down about 2 MPH as a starter and that could be the reason for the lack of swing and miss. But I can help but wonder if the elimination of the 4-seam has handcuffed Whitlock in strikeout counts. 

Swapping out the Slider for the Sweeper

2023 was the year of the sweeper. It seemed like every pitcher started throwing one and television broadcasters started calling pitches using the term sweeper. Whitlock followed the trend and added a sweeper. Back when Whitlock had his dominant 2021 season, Whitlock was throwing a slider. The slider back in ‘21 only had 4.4 inches of horizontal break but 38.4 inches of vertical drop. The slider was an effective pitch for Whitlock that year as hitters only hit .216 off of it. I have to think the slider looked a lot like his fastball or sinker with little horizontal drop and the fact that Whitlock threw the pitch at 83.7 MPH. 

Last season, Whitlock swapped out the slider for the ever popular sweeper. Whitlock’s sweeper was thrown with an average 9.4 inches of horizontal break and 47.2 inches of vertical drop. It was thrown at an average velocity of 79.6 MPH. The sweeper was an effective pitch last season as opposing hitters only hit .167 off of it and Whitlock had a 25% put away percentage with the sweeper. 

I am not doubting that Whitlock has an above average pitch in the sweeper. My question is can hitters differentiate between the sinker and sweeper easier than the sinker and slider combo. Last year, opposing batters hit .331 off of Whitlock’s sinker. The shape of the sweeper and the velocity difference could allow opposing hitters the opportunity to differentiate between Whitlock’s pitches. So many pitchers are making these arsenal changes in pitching labs. If there was a significant difference in the shape of Whitlock’s sinker and his new sweeper, you would think they would tweak it until they get it right. But it does make you wonder if Whitlock was actually more effective with the slider. 

When Garrett Whitlock is locked in, he is one of the best relievers in all of baseball. Returning to the bullpen permanently could allow Whitlock to rediscover his dominant form. Returning back to some of his 2021 arsenal could also help him rediscover that dominant form that Red Sox fans fell in love with a few years ago.