Alek Jacob, Stuff+, & The Power Of Pitch Mix

Relievers are often known for having a small arsenal. As Padres fans will well know, the great Trevor Hoffman relied on his changeup. For Mariano Rivera, it was the cutter. Even in today's game, high-leverage relievers can be elite with a single pitch, just ask Robert Suarez, who rode his fastball to great success, and the nickname "Bobby Fastballs", in 2024 as the Padres' closer. 

It isn't uncommon for relievers to rely on their one or two dominant pitches to great success, like Jeremiah Estrada, who leans heavily on a fastball (121 Stuff+, 64% usage) and splitter (129 Stuff+, 19% usage). Some relievers throw a starter-like repertoire including sizable usage of less stuff-y pitches, like Twins starter-turned-reliever Louis Varland, who throws five pitches, including a slider (98 Stuff+, 12% usage) and changeup (77 Stuff+, 10% usage), which grade out less favorably. For those unfamiliar with Stuff+, it is a model-based measure of pitch shapes produced by Eno Sarris, available on FanGraphs, and calibrated such that a Stuff+ of 100 is league-average and 10 is one standard deviation (note: for simplicity and because of ongoing tweaks to Stuff+, we won't dive deeper into pitch-level averages, which are not identically 100 but end up currently as 98 for a fastball, 101 for a sinker, 94 for a changeup, etc.).

This means that Estrada throws a fastball with two standard deviations better than average and a splitter with three standard deviations better than average. At the same time, Varland's changeup, at 77 Stuff+, is two standard deviations worse than average. Despite relying on very different arsenals, both Varland (28.9% K-BB%, 1.97 SIERA) and Estrada (30.6% K-BB%, 2.18 SIERA) are both effective relievers, in large part because Varland works in a total of five pitches including a 129 Stuff+ knuckle-curve and a 113 Stuff+ fastball to complement his less stellar changeup and slider. Varland relies on a broader mix of pitches to be effective, while Estrada relies on elite stuff on two pitches.

But what if you had a pitcher with a wide arsenal of "plus" secondary pitches and elite stuff on their fastball? Enter Padres reliever Alek Jacob and some of the off-season improvements that got him there, for an answer to that question. 

Alek Jacob throws four pitches, in order of usage: a fastball (121 Stuff+, 37% usage), changeup (109 Stuff+, 34% usage), sweeper (110 Stuff+, 15% usage), and sinker (100 Stuff+, 14% usage). Jacob has added 2.8 inches of rise (induced vertical break or iVB) on his fastball, 3.6 inches of arm-side run on his changeup, 1.4 inches of arm-side run on his sinker, and 6.5 inches of iVB on his sweeper. The differences in these shapes are apparent in his Movement Profile graphics from Baseball Savant.

Jacob has added arm-side run to his seam-shifted wake pitches (sinker and changeup), increased the vert on his fastball, and completely reworked his sweeper.

The shaded dots above represent league-average movement for that pitch, while the solid dots show Jacob's pitches and have sizes scaled to usage. In addition to adding iVB to his fastball, it has a bit less arm-side run and has jumped up in usage. The changes to his fastball, sinker, and changeup shapes help give Jacob more shape separation between the fastball and sinker, while maintaining a nine mph velocity separation between the sinker and change. His sweeper looks like an entirely new pitch, sacrificing a bit of glove-side break for a massive 6.5 inches of iVB, and he uses that extra vert to spot the opposite corner of the zone from his changeup. 

Jacob's changeup (arm-side + dive) and sweeper (glove-side + rise) have complementary shapes, which are reflected in their usage heatmaps.

In 2024, Jacob filled the zone with the sinker and threw the fastball at the top of the zone for a change of pace. In 2025, he now features the fastball as his go-to pitch, filling up the zone with that pitch and tunneling his sinker, changeup, and sweeper off of that pitch to complement it. Those spots are down and arm-side with the changeup, up and glove-side with the sweeper, and arm-side with the sinker. In short, he has made his best pitch better, now throws it more than any other pitch, and plays his secondaries off it more effectively.

Jacob's heatmaps for: 2024 fastball (top left), 2025 fastball (top right), 2024 sinker (bottom left), 2025 sinker (bottom right).

Jacob's offseason adjustments have paid off, allowing him to contribute quality innings to a talented Padres bullpen full of existing stars and other promising 26-year-olds (Alek Jacob, Jeremiah Estrada, Adrian Morejon, and Omar Cruz, who made his debut at Petco earlier this season, are all just 26). 

While Morejon and Estrada jump off the page for reasons of their own, Jacob also finds himself among some elite company. He throws four pitches of at least 100 Stuff+ and with at least 10% usage, which only four other relievers in the league can say: Yimi Garcia (TOR), Hoby Milner (TEX), Reed Garrett (NYM), and Seranthony Dominguez (BAL). Unlike these relievers, who are all in their 30s and mostly pitching high-leverage innings, Jacob is young, team-controlled, and figures to continue to build on these arsenal tweaks in the coming years. Padres fans should not be surprised if he begins to take on higher-profile spots in 2026 and beyond, either moving to a higher-leverage role or potentially trying to stretch out as a starter.