Improved sinker has helped Elvis Peguero ascend in Brewers' bullpen

The Brewers have won five of seven games on their current road trip, and the bullpen has played a pivotal role in that recent success.

Perhaps no reliever has delivered bigger outings than Elvis Peguero, who has ascended into a high-leverage role amid the inconsistent performance of Peter Strzelecki.

Peguero has appeared five times in the last six days. He picked up his first career save in Sunday’s extra-innings series finale against the Cleveland Guardians. He collected holds in each of the Brewers’ three wins against the New York Mets. On Thursday night, Peguero inherited a bases-loaded, one-out jam in the seventh and promptly induced an inning-ending double play to preserve a one-run lead.

Peguero’s best pitch has always been his hard slider. It’s one of baseball’s firmest sliders, averaging over 90 mph. While it was not a dominant pitch during his brief time with the Los Angeles Angels last season, it induced whiffs at a 31% clip and held hitters to a .297 xwOBA.

The problem was Peguero’s sinker. Despite the pitch sitting in the upper-90s with above-average movement, opponents teed off on it. They batted .393 with a .487 wOBA against the sinker.

The ineffectiveness of the sinker made Peguero overly reliant on his slider. He threw his breaking ball 63% of the time with the Angels in 2022 and turned to his sinker just 37% of the time.

While slider usage continues to trend upward across Major League Baseball and fastball usage continues to drop, the ability to establish a fastball remains an essential component of pitch sequencing and keeping hitters off balance. Peguero lacked that ability.

That has changed since he joined the Brewers in the Hunter Renfroe trade last November. Peguero’s sinker has experienced a complete one-eighty in its effectiveness. Opponents are hitting just .245 with a .288 wOBA against it in 2023. The average exit velocity when hitters put the sinker in play has fallen to a respectable 89 mph.

The turnaround stems from improvements Peguero has made to the shape of his sinker. His average sinker velocity has dipped slightly from 96.4 to 95.5 mph, but he has added nearly four inches of vertical movement to the pitch. In other words, his sinker is sinking much more than it did in previous seasons.

Peguero always had the ability to generate this much sink. He is a unicorn of sorts in that he throws hard but has one of the lowest fastball spin rates in baseball.

The lower the spin rate of a sinker, the more gravity pulls it down as it approaches the plate, giving the pitch more sinking action.

This trait presumably drew the Brewers to Peguero, and they have helped him harness his unique ability to craft a unique pitch.

Peguero’s heater now features elite sink for someone who throws as hard as he does. When adjusting for average pitch speed and extension, it has nearly six more inches of vertical break than the average sinker.

When plotting sinker movement relative to velocity, Peguero stands out. The red dot on the chart below represents his sinker.

Only one pitcher who has thrown enough sinkers to qualify for the chart above throws a sinker at a greater velocity with more vertical movement. That hurler is Baltimore Orioles setup man Yennier Cano, who possesses arguably the best sinker in baseball and owns a 1.14 ERA in 39 ¹⁄₃ innings this season.

However, that ranking by standard velocity is misleading. Because the six-foot-five Peguero generates nearly seven feet of extension, he releases the ball much closer to home plate than most pitchers. By cutting down on the amount of time a hitter has to react to the pitch, Peguero’s sinker plays as if it were thrown a tick harder than its actual release speed.

The average perceived velocity of Peguero’s sinker is 96.7 mph. Cano’s is 94.2 mph. While Cano still generates much more sink, Peguero brings more velocity from the hitter’s perspective.

Peguero’s new demon sinker has not just induced more weak contact. It has missed bats entirely at an impressive rate.

In 2022, Peguero’s sinker yielded a whiff rate of just 10%. It was the main culprit behind his low strikeout rate (16%) and inability to put hitters away.

This year, Peguero’s sinker has induced whiffs on 21% of swings. The league average whiff rate against sinkers is 15%.

Here’s Peguero fanning Starling Marte on Monday night with a power sinker down and in.

Here’s a similar pitch to fan Gabriel Moreno last week.

Unlike his old sinker, Peguero’s improved fastball is a serious player in his pitch mix.

Peguero has refined his approach to a nearly even combination of sliders and sinkers. This enables him to cover both sides of the plate and keep hitters guessing. The sinker and slider play exceptionally well off one another, with each making the other more effective.

Some minor tweaks to Peguero’s slider have also paid dividends. He has added about two-and-a-half inches of vertical break to his breaking ball, and its whiff rate has increased from 31% to 42%.

In addition to the strong results of his sinker, pitch modeling metrics are sold on the changes Peguero has made to its shape. The Stuff+ rating of Peguero’s sinker has improved from 85 in 2022 to 94 in 2023.

Peguero is the latest success story in what has become a common occurrence in Milwaukee. Under the tutelage of the Brewers’ big-league pitching development staff, he has elevated his already-enticing arsenal by improving the shapes of his pitches. This has opened up new ways for him to attack hitters. The results have followed.

Statistics courtesy of Baseball Savant and FanGraphs.