Peter Strzelecki must find the right pitch mix

It took Peter Strzelecki all of eight pitches to retire a trio of threatening Padres hitters in order in a scoreless eighth inning on Sunday.

Setting up closer Devin Williams in an eventual 1-0 Brewers win, Strzelecki made quick work of Matt Carpenter, Xander Bogaerts, and Manny Machado on a flyout sandwiched between two soft ground balls.

The Brewers planned on Strzelecki playing an instrumental role at the back end of their bullpen, and so far, he has answered the call. He has thrown 7 ¹⁄₃ scoreless innings, extending a scoreless streak that began last September and now stands at 16 ²⁄₃ innings.

While Strzelecki has the stuff to excel in a high-leverage role, his early results are a bit deceiving. He’ll need to make some adjustments to continue finding success.

Strzelecki has a new pitch this year. He confirmed last week that he added a sinker in spring training.

The Brewers approached Strzelecki over the winter about developing a sinker. Given that he throws with a low three-quarters arm slot and already has natural arm-side run on his four-seam fastball, it stood to reason that Strzelecki could throw a good sinker.

Strzelecki can indeed throw a good sinker. Statcast says the new pitch has averaged 32 inches of sink so far. That’s an additional four and a half inches of vertical movement compared to the typical sinker thrown at a similar velocity and release point.

Strzelecki has one of the heavier sinkers in the game, which has helped close one of the gaps in his profile as a pitcher.

While he did not allow a ton of hard contact last year, opponents did manage a 26.7% line drive rate against him. Unlike other kinds of batted balls, liners usually go for hits (68% of the time in 2022 and 70% this year). The more line drives a pitcher allows, the harder it becomes for him to avoid damage on balls in play.

Strzelecki has thrown his new sinker 22% of the time thus far. Opponents have recorded just one hit against it in nine at-bats. It has held them to an average exit velocity of 83.4 mph and induced ground balls at a 78% rate.

The pitch has transformed Strzelecki into a weak contact machine. He has limited opponents to an 18.2% hard hit rate and 84.5 mph average exit velocity. His ground ball rate has doubled from 31.1% in 2022 to 63.6% in 2023. His line drive rate is down to a minuscule 13.6%. Those are all elite marks.

However, the sinker has been a double-edged sword of sorts for Strzelecki. While his quality of contact metrics have dramatically improved, his swing-and-miss numbers have worsened substantially.

Missing bats was Strzelecki’s greatest strength last season. He punched out 27% of hitters he faced, and each of his three pitches—four-seamer, slider, and changeup—induced whiffs on at least one-third of swings.

The four-seamer and slider are still swing-and-miss pitches. They have produced whiff rates of 33% and 25% this year, respectively.

Meanwhile, opponents have yet to swing and miss at Strzelecki’s sinker.

His strikeout rate has been more than cut in half to 11.5%. The same is true of his swinging strike rate, which has shrunk from 12.2% to 5.7%.

The disappearance of strikeouts from Strzelecki’s game is not exclusively due to his sinker. The put-away percentage on his slider has dropped from 25% to 15%, meaning he is recording fewer strikeouts on two-strike sliders. That number figures to tick up as the sample size grows.

Furthermore, while Strzelecki’s sinker usage is up and his four-seam usage is down across the board, he is still using effective sequencing against right-handed batters.

Source: BrooksBaseball

Strzelecki has continued to rely on his swing-and-miss stuff in most counts but has turned to the sinker when he falls behind. When pitchers fall behind, hitters start looking for pitches in the zone to punish, so using the pitch with the best chance of missing the barrel and inducing a ground ball makes sense.

All three of Strzelecki’s strikeouts have come against right-handed batters. That translates to a 23.1% strikeout rate against right-handers in a tiny sample size. At this stage in the season, that’s not concerningly far from his 28.7% mark last year.

Meanwhile, Strzelecki has yet to record a strikeout against a left-handed batter after punching them out at a 24.1% rate last season. A look at his pitch usage against lefties makes it clear why this has been the case.

Source: BrooksBaseball

This is where the sinker bears greater responsibility for the lack of strikeouts. In 2022, Strzelecki attacked lefties with his four-seamer, using both the fastball and the changeup as put-away pitches. This year, Strzelecki is only using his four-seamer a quarter of the time in such matchups, including situations in which he can pitch for a strikeout.

Some of that is due to throwing more changeups. As time progresses, Strzelecki will start picking up strikeouts on such pitches. At the same time, the impact of the sinker is apparent.

Five left-handed at-bats against Strzelecki have ended on his sinker thus far, the highest total among any of his pitches. Just one at-bat has concluded with a four-seamer.

None of this is to say that Strzelecki should scrap his sinker. It’s a great pitch that induces a ton of soft contact, a skill that will serve any pitcher well.

However, becoming overly reliant on converting balls in play into outs can be a dangerous game. As a high-leverage reliever, there will be times when Strzelecki must pitch for strikeouts. He certainly has the swing-and-miss stuff to do it. Failing to take advantage of that ability will hurt his results and prevent him from reaching his potential.

Adding a sinker has given Strzelecki a well-rounded arsenal and allows him to retire hitters in different ways. Now he must learn how to utilize each of his pitches to achieve the best combination of strikeouts and weak contact.