What about a 110 mph fastball?
Hunter Greene hit 105 in a B game in ST this year, 11o will probably be hit within a decade
Someone throwing a 110 mile an hour fastball has probably already happened: Nolan Ryan.
There's a great documentary (was on Netflix, probably on Prime now) about Fastballs. They talked about the methods attempted to measure pitchers.
Nolan Ryan got clocked at 100.8 mph in the ninth inning of a start for the Angels in the late 70s. But they measured the speed AT HOME PLATE, which is not how they do it now. (and the tech was terrible). They measure the speed of MLB pitchers now using StatCast measurements 10 feet from the pitching rubber, not the plate.
When you account for the 50 feet of drag, Ryan's 100.8 mph pitch would clock in at like 108 today. And that was his like 150th pitch of the night.
Pitching Ninja lined up some of the famous Nolan Ryan clips from the 70s, versus Chapman and Jordan Hicks 105 mph pitches and did the side-by-side, and they look pretty much the same. But again, those two modern guys were closers, and Ryan was a starter. And all the famous Ryan clips are from late in games.
Ryan was a superhuman beast. His last MLB pitch ever, at age 46 was using more modern measuring tech... it clocked in at 96 mph, and on which his frayed UCL finally snapped.
Everyone trying to "mythbust" Ryan hitting 108 has failed to do so. And pretty much every clip they use is when he was in his 30s. When he was in his 20s, he probably hit 110.