For more than a decade, Aroldis Chapman built his career around an overpowering triple-digit fastball. However, just when many believed the Cuban left-hander was entering the inevitable decline that comes with age for veteran relievers, the opposite happened: he reinvented himself in Boston thanks to a crucial adjustment to his pitch mix.

The veteran closer not only maintained elite velocity throughout 2025 and 2026, but he also made significant improvements in getting ahead of hitters. According to FanGraphs, Chapman dramatically increased his first-pitch strike percentage, a change that coincided with the growing use of his sinker.

That pitch ultimately became the foundation of his resurgence.

Aroldis Chapman’s sinker changed the way he attacks hitters

For most of his career, Chapman relied almost exclusively on his four-seam fastball to overpower opponents. Now, his sinker has become a devastating weapon that forces hitters into impossible split-second decisions, according to Baseball Savant.

The key lies in the visual deception between the two pitches. Both the four-seamer and the sinker come out of the exact same release point and travel close to 100 mph, but they behave very differently as they approach home plate. While the four-seam fastball stays on a flatter plane, the sinker dives sharply at the last moment. (See attached graphic.)

The results have been remarkable.

Entering the 2026 season, Chapman was throwing his sinker nearly as often as his four-seam fastball—something unimaginable during the first half of his career. The accompanying chart illustrates how his four-seam usage has steadily declined while the sinker has become his primary weapon. MLB highlighted that this combination allowed him to attack both right-handed and left-handed hitters with far greater precision.

The numbers fully support the adjustment. FanGraphs shows that Chapman’s sinker outperformed his traditional four-seam fastball in both opponents’ batting average and swing-and-miss rate throughout 2025 and 2026.

Even more impressive, Chapman no longer relies solely on overpowering velocity. His walk rate dropped significantly in 2025, addressing what had long been considered the biggest weakness in his profile.

A sinker unlike most across Major League Baseball

Perhaps the most fascinating aspect of Chapman’s evolution is that his sinker doesn't function like the typical sinker thrown around Major League Baseball. Most pitchers use the pitch to induce weak contact and ground balls. Chapman, however, uses it as a strikeout weapon.

That distinction changes everything.

His sinker isn't designed simply to generate grounders—it is designed to overpower hitters and miss bats. During 2025, the pitch generated a significantly higher strikeout rate than his four-seam fastball, establishing itself as one of the most effective offerings in Boston’s bullpen.

The context makes the story even more impressive. Chapman arrived in Boston with questions surrounding both his durability and consistency, yet he responded by producing one of the finest seasons of his career. Multiple baseball analysts noted that he finished 2025 with an ERA near 1.00, an elite WHIP, and one of the highest WAR totals ever produced by a reliever of his age.

Even among analytical and fantasy baseball communities, many fans once again began placing Chapman among the elite closers in Major League Baseball.

What makes this transformation truly remarkable is that Chapman evolved without sacrificing the qualities that made him a legend. He still throws at astonishing velocities for a pitcher approaching 40 years old, but now he does so with greater intelligence, a more diverse arsenal, and a much deeper understanding of how to attack today's hitters.

His fastball remains terrifying. His sinker, however, is the pitch that returned him to baseball's elite.