What's Causing the MLB Pitcher Injury Epidemic?

In 2004, fastball usage was 62.6%. In 2025 it's 47.8%. Slider usage increased from 13.6% to 22.4%, and cutter usage went from 1% to 7.5%. I combined sliders and cutters in the chart above. Bascially the combined use of sliders and cutters has doubled over the last 22 season.

Note that curveball and changeup usage has remained relatively stable, ranging between 9-11% each, although the last two years have seen a slight dip in those two pitches as well. Split-finger use has more than doubled since 2022, but still represents just 3.8% of all pitches thrown.

EVER-INCREASING VELOCITY

Average fastball velocity has increased from 90.1 in 2004 to 94 MPH today. Before anyone argues this increase is caused by measurement differences, that issue was already addressed by FanGraphs and they made the adjustments to account for measuring at release point versus 55 feet in the historical data prior to 2017 when the new system came on line.

Note also that pitchers are throwing every pitch harder, sliders +1.9 MPH, cutters +3.3, curveballs +4.7, and changeups +4.9.

OTHER FACTORS

The above two factors might seem like an over-simplification to some. There are certainly other potential factors contributing to the increase in injuries. But those are the two biggest and most important reasons.

Pitch Clock: The MLBPA has claimed that the pitch clock has led to more pitcher injuries, but that data is inconclusive. It should be noted that several decades ago, the average time between pitches was usually under 15 seconds without men on base. Just use a stopwatch and check out old YouTube videos.

But pitchers weren't throwing as hard then, and threw mostly fastballs. Perhaps the pitch clock is exacerbating the effects of the added velocity and torque from too many breaking pitches.

Youth Baseball

By the time a young pitcher enters a major league organization, they've been throwing at max effort velocity for year, trying to impress scouts. Young amateur pitchers are throwing nearly year round, between youth leagues, travel ball, school teams, etc. They're simply throwing too hard for too long before they ever turn professional.

Solutions

Hitters are too good today to get out easily. Hitters in the past were great too. But if you go back and look at the mechanics and footwork in videos on Youtube, you see a lot more movement, shifting of feet, and off-balance swings from odd-looking stances. Lineups prior to the middle 80's seldom had more than three or four longball threats. Now every lineup has eight hitters who can take you deep on any pitch.

The best ways to change the game if MLB wants to keep pitchers healthy are to deaden the baseball and institute thicker bat handle minimums. That will force most hitters to adjust to a more contact-oriented approach, and leave the slugging to the truly big power-hitters.

In turn, that will allow for pitchers to navigate lineups without needing to throw quite as hard or use as many pitches per at-bat.

Finally, in order to get pitchers to pitch to contact and not rely on trying to strike everyone out, tie contracts to innings pitched incentives more closely than they currently do.

These are all steps MLB could take if they are interested in protecting pitcher health. However it's unlikely these changes will take place. The league and its fans are addicted to the home run, and it's unlikely that we go back in time. So the churn and burn through pitcher arms will continue for the foreseeable future.