Yep, Ted Williams lays this out beautifully in The Science of Hitting. From the book:
To add to this, Joey Votto explained how pulling the ball requires better timing as well: (1) It shrinks the sweet spot of the bat and (2) you also have less time to react as you must get your bat out in front of you to meet the ball.
Vlad doesn't pull the ball in the air much at all and it's no surprise because it's already hard to do for any hitter for the reasons Votto mentioned, but it's even harder for Vlad because with his downward swing has his bat path in the ball's trajectory even less than everyone else. He's got to be perfect to pull a ball in the air.
Despite all this, he's been able to make it work, even if it's frustrating because he could show more power. But this year, something is happening and I'm not quite sure why.
I think he's simply (1) having a down year and all the mental struggles that come with that but (2) it's exacerbated by the league figuring him out.
If you look at his zone percentages from previous years and compare them to 2026, pitchers are throwing him up more instead of down. Attack angles on pitches up are always worse for every hitter than they are for pitches down, but I wonder if with Vlad it gets to the point that a ball up just breaks his swing completely.
Someone like Springer who has as 10 degree attack angle still has a 6 degree attack angle on a pitch up in the zone. But when Vlad has a 1 degree attack angle, he has a -4 degree attack angle on pitches up. You just can't do much with a ball when you are swinging down like that. So pitch Vlad up and he's cooked?
https://baseballsavant.mlb.com/savant-player/vladimir-guerrero-jr-665489?stats=statcast-r-zones-mlb