MLB Pitch Clock 2023: How Did It Impact Game Outcomes?

photo courtesy: CNN

Say what you want about the MLB pitch clock and the new rules this past season. The desired effect--to shorten the game--was achieved.

Time of MLB games dropped 

Pace of play (time in between pitches has also dropped)

What about the game itself? 

Larger bases and limited throws to first base with a runner on strongly suggested stolen bases success rates would be higher.  

Shift elimination helped bring the balls in play batting average (BABIP) for left handed hitters in line with right handed hitters.

Weighted on base average (wOBA) also rose.

All of these changes were expected as a result of the rule changes and the addition of the pitch clock. Yet many aspects of the game such as balls in play and the high strikeout totals -- to name a few --remained pretty much the same. 

The 16 charts below illustrate how the core of the game has changed over the last 15 years or so.

Three plate outcomes (walk, strikeout, homerun) rates have been rising since roughly 2010 peaking in 2020 with a small drop in 2021 and 2022 with a jump in 2023 AFTER the rule changes.

Rate of balls in play started a sharp decline in the late 2000s hitting a low of 67.3% in 2020. A small increase in the last 3 years but no where to the 1990s/early 2000s levels.

Strikeout rates saw a similar rise at roughly the same time. Again little change last season.

Swing strike percentages have hovered around 19% over the last 5 seasons. The increase started around 2010.

The percentage of pitches swung at outside the strike zone started rising in the mid/late 2000s. Rates at 18.1% in 2002, 21.5% in 2005 jumping to near 30% by 2010 where they've stayed ever since.

Contact on pitches outside the strike zone also way up starting in the late 2000s with the rate steady since 2010.

Percentage of pitches inside the zone dropped at roughly the same time.

Flyball rates have rose since early 2010s lows back to early 2000s levels,

Home run rates per plate appearance stayed the same until roughly 2015 then a 35% jump between 2015 and 2019. HR per plate appearances have remained elevated since.

As home run rates rose, slugging percentage on flyballs also rose through 2019. Since then, then have dropped to early 2010s levels.

Percentage of runs via home runs rose in 2023. Overall levels remain at 2016 levels.

Slugging percentage AFTER 2 strikes started falling in the late 2000s. A few brief jumps but nothing sustainable.  Average "After 2 strike slugging" remains steady over the last decade.

Interesting to note that slugging with runners in scoring position, after a drop between 2006 and 2014, has jumped back to mid 1990s levels.

On top of of offensive changes over the last 10-15 years, pitching speed and frequency has shifted. Velocities are higher across the board.  

Fastball frequency is down more than 12%.  Sliders are up almost 8%. Cutters are up 5% versus a decade ago.  However curveballs and changeups are unchanged.

All of this data points to system wide changes to how game actions are executed. These changes have occurred over almost a full generation.  As of this writing, the 2023 rule changes/pitch clock additions changed base running and defensive alignments. Yet players' approach at the plate and the way pitchers pitch remains so far unchanged. The game is faster, pace of play is down yet the type of baseball we've been watching in recent years remains the same.  Will this change in the next 5 -10 years?