Yu Darvish's Pitching Evolution (2021-2025): A Statcast Data Analysis

#baseball #mlb #statcast #datascience

Introduction

In November 2025, Yu Darvish underwent UCL (ulnar collateral ligament) surgery, ruling him out for the entire 2026 season.

Over his five years with the San Diego Padres (2021-2025), his game appearances declined from 30 to 15. Looking at the Statcast data from this period, the numbers suggest significant shifts in his pitch mix and pitching style.

In this article, I use pybaseball + DuckDB to pull five seasons of Statcast data and examine how his pitch selection, velocity, and whiff rates changed over time. Note: This is purely a data-driven exploration of observable trends -- it is not intended to make definitive claims about the pitcher's intentions or decision-making.

The Google Colab notebook used for this analysis is linked at the bottom of the article.

Five-Year Timeline

Before diving into the data, here is a brief timeline of key events during this period.

Year	Age	Games	Pitches	Notes
2021	34-35	30	2,773	First season with the Padres
2022	35-36	30	2,971	Peak FF velocity (95.0 mph)
2023	36-37	24	2,219	Participated in WBC for Japan (Feb camp onward) -- delayed season start. Shut down in August with olecranon stress reaction
2024	37-38	16	1,264	Multiple injuries (neck, hip, elbow). Placed on restricted list (family matters). Returned in September
2025	38-39	15	1,160	Started season on IL with right elbow inflammation. Returned in July after 269 days. UCL surgery in November

Elbow-related injuries have been a recurring theme since 2023. Let's see what changes appear in the data from this period.

Data Collection

from pybaseball import statcast_pitcher
import duckdb

PITCHER_ID = 506433  # Yu Darvish
YEARS = [2021, 2022, 2023, 2024, 2025]

dfs = []
for year in YEARS:
    df_year = statcast_pitcher(f'{year}-03-01', f'{year}-12-31', PITCHER_ID)
    df_year['season'] = year
    dfs.append(df_year)

df_raw = pd.concat(dfs, ignore_index=True)

# Regular season only
con = duckdb.connect()
df = con.execute("SELECT * FROM df_raw WHERE game_type = 'R'").df()
# -> 10,387 pitches (5 seasons combined)

Important: Filtering by game_type = 'R' is necessary to exclude spring training and postseason data.

Pitch Mix Changes

Here is how his pitch usage rates shifted over five seasons.

Pitch	2021	2022	2023	2024	2025	Change
SL (Slider)	31.0%	31.5%	17.7%	23.3%	14.9%	-16.1%
ST (Sweeper)	22.8%	15.4%	18.6%	14.0%	9.1%	-13.7%
FF (Four-Seam)	22.1%	25.5%	16.7%	18.4%	16.0%	-6.1%
SI (Sinker)	8.3%	8.5%	18.6%	17.1%	20.0%	+11.7%
CU (Curveball)	4.6%	4.0%	5.0%	8.6%	15.4%	+10.8%
FC (Cutter)	2.5%	4.3%	8.9%	4.6%	12.2%	+9.7%
FS (Splitter)	4.9%	7.4%	7.7%	4.0%	10.6%	+5.7%

In 2021, slider (31%) + sweeper (23%) = 54% of all pitches, making horizontal breaking balls the core of his arsenal.

By 2025, that combined share had dropped to 24%, while sinker (20%), curveball (15%), and cutter (12%) usage all increased.

The 2023 Shift

The 2023 data stands out. SL usage dropped from 31.5% to 17.7%, while SI jumped from 8.5% to 18.6%. That season was marked by a delayed start due to WBC participation and an August shutdown for an olecranon stress reaction, both of which may have contributed to the shift in pitch selection.

Generally speaking, sliders and sweepers are considered to put relatively more stress on the elbow. Sinkers, by contrast, involve a more natural arm motion, and curveballs rely more on speed differential. This shift could reflect an adjustment for elbow health, though strategic pitch-sequencing decisions and other factors may also be at play.

Velocity Trends

While the pitch mix changed substantially, average velocities for each pitch type remained relatively stable.

Pitch	2021	2022	2023	2024	2025	Change
FF	94.5	95.0	94.7	94.1	93.9	-0.6 mph
SI	94.0	94.7	94.3	93.6	93.4	-0.6 mph
SL	86.2	86.0	85.7	85.9	85.7	-0.5 mph

A decrease of 0.6 mph on the four-seam over five years is not particularly dramatic. The pitch mix changes appear to be driven by factors other than velocity loss -- possibly condition management, strategic adjustments, or a combination of both.

Velocity by Inning

While average velocity held up, the pattern of velocity drop-off as games progressed tells a different story.

Year	1st Inning	Final Inning	Change	Latest Inning with Data
2021	94.5	95.0	+0.5	7th
2022	94.9	94.4	-0.5	8th
2023	94.9	93.7	-1.2	7th
2024	94.4	93.3	-1.1	7th
2025	94.2	92.8	-1.4	6th

In 2021, Darvish maintained his velocity through seven innings. By 2025, the data shows a 1.4 mph drop by the sixth inning. That said, the 2024-2025 data includes starts made shortly after returning from injury, which likely affects these numbers.

Whiff Rate Changes

Whiff rate = swinging strikes / total swings (whiffs + fouls + balls in play).

Pitch	2021	2022	2023	2024	2025
FF	30.0%	19.4%	15.4%	13.0%	14.3%
CU	29.2%	26.8%	44.0%	41.1%	33.8%
FS	31.9%	34.4%	38.9%	34.5%	26.6%
SL	26.2%	24.4%	22.7%	26.6%	18.3%
ST	21.2%	24.2%	25.8%	25.0%	32.6%

The four-seam whiff rate declined from 30.0% to 14.3%, while the curveball's whiff rate peaked at 44.0% in 2023. The shift in which pitches generated the most swings and misses appears to correlate with the changes in pitch selection.

Pitch Selection with Two Strikes

The same trend is visible in his two-strike pitch selection.

Year	1st	2nd	3rd
2021	ST 25.6%	FF 24.4%	SL 15.4%
2022	FF 32.8%	FS 17.6%	ST 16.1%
2023	FF 22.4%	FS 17.9%	SI 15.6%
2024	FF 21.2%	SL 19.9%	ST 15.1%
2025	CU 21.8%	FS 17.2%	FF 15.1%

In 2021-2022, the four-seam and sweeper were his primary putaway pitches. By 2025, the curveball had become his most-used two-strike offering.

Summary

Across Yu Darvish's five seasons with the Padres, the Statcast data reveals the following trends:

Pitch mix: A gradual shift from slider/sweeper-heavy (2021-2022) to sinker/curveball/cutter-heavy (2024-2025)
Velocity: Average velocity for each pitch type declined only about 0.5-0.6 mph over five years
Velocity by inning: Late-inning velocity drop-off appears to have increased year over year
Whiff rate: Four-seam whiff rate declined, while curveball whiff rate increased
Putaway pitch: Two-strike pitch selection shifted from four-seam/sweeper to curveball

The changes seem to have accelerated around 2023, coinciding with his WBC participation and the olecranon stress reaction. The data suggests that changes in physical condition may have influenced his pitch selection over time.

Note: The 2024 (16 games) and 2025 (15 games) seasons have small sample sizes, so the numbers should be interpreted with caution. Whiff rates for less frequently thrown pitches are especially volatile with fewer observations. Additionally, the data includes starts made shortly after injury rehabilitation, which may not reflect typical performance levels.