Seems like 2 things going on at once. The MLB statcast equipment which reduced speed, and pitchers changed strategy to focus more on raw speed.
From Grok:
There was no change in 2015 itself for official statistics – 2015 still used the old “out-of-hand” measurement.
The big change happened for the 2016 season, when MLB switched to reporting velocity at 50 feet from the plate using the new Statcast/TrackMan radar systems that had been installed league-wide in 2015.
So when you see articles saying velocity “dropped” in 2016, it’s almost entirely because of this measurement change, not because pitchers suddenly got slower.
@MattRexroad It was the brain child of Pat Gallagher with the giants, the anti mascot. Also came up with the CROIX DE CANDLESTICK
Crazy like a crab https://t.co/ecZ6hG2aWb