When a pitcher needs to throw a baseball he requieres a lot of strenght and control, being on the ground allows for the control and being able to transfer the momentum from the body to the ball.
Now, how much of that force and control could be used if the pitcher is floating in micro-gravity or zero g. How much force could it be transfered to the ball?
And according to Newtons 3rd law, how would the pitcher and the ball move in space?
The speed of the ball will not depend on gravity to any significant degree. Gravity provides a downward acceleration, so it increases speed not decreases it.
So if we like a pitcher with no space suite we need to have an atmosphere. A space suit will significantly hinder the motions.
The speed at the point the ball leaves you to hand depends on the speed of your hand so the limitation is your body and a small amount of air resistance. In zero-g you can stand on your feet if you were just floating in the air the speed you can throw a ball should be decreased because your muscles will not just move the ball but also result in your body rotation so the speed is decreased, This happens even if you just use you are because is not inline with you center of mass.
The normal way to throw a baseball is for you to rotate your upper body relative to the ground, If you float in zero-g the same motion was rotated your lower body in the opposite direction so the upper body rotate slower. So the ball will go slower than down on earth.
The accuracy will also be reduced because releasing the ball at the right moment will be harder, there are more factors that are relevant like the exact position of all of your body during the throw, Because you do not rotate on the ground is a lot less relevant.
The pitches also take a step and start standing on the rear foot then during the throw step forward and end up on the forward foot. During this forward motion, the body is accelerated by gravity. This will not work in zero-g. You can strap your feet in place. So the result of throwing a ball in zero-g is like the exact same as if you do it with one of both feet fixed on the ground or strapped to something. I suspect that the speed will be a lot lower than on earth.
How about accuracy? Gravity is a constant force the speed of the ball is not the same in each throw is there will be differences in how it accelerates the ball. But it gets more complicated because the ball spin and it produces forces on the ball. A backspin will create an upwards force that counteracts some of the gravity on earth and make the ball move down slower. In zero-g that will make the ball move up. So it might the simpler to throw high accuracy ball on zero-g or it might be harder. A relevant factor will be if you compare to out in the open on earth or indoors on earth. There is a lot less wind indoors the same will be the case in any zero-g environment on earth. There is an air current in ISS because of fans but you can turn them off.
You do not need the same air pressure and earth seal level it can be reduced. But the same can be done on earth with gravity, vacuum chamber exists so pressure can be reduced until it kills the pitcher. So any result of lower air pressure is independent of gravity.
If you are out on a vacuum you need a spacesuit and they resist motion and limit it. They also add mass to your body you need to accelerate when you for example move your arm. Air resistance do not have a significant effect when you throw the ball so the result will be the speed of the ball when it leaves your hand is significantly reduced.
There is no air resistance to the ball will no slow down so at some distance from the pitches the ball will move faster than it would do in an atmosphere. I doubt that distance is less than the normal distance from the pitcher to batter. You can create throw the ball a long distance.
For accuracy, the spacesuit will make it harder to throw the ball in as exact initial direction but after that, it will fly in a straight line. So because the ball does not slow down no arch is needed and wind and spin have no effect at some distance the accuracy will likely be higher.
So the answer is a lot it depends
It would depend on how much the pitcher weighed. With a conventional pitching motion, the pitcher’s center of gravity would move backward at a speed which was inversely proportional to his weight, and would rotate backwards around his center of gravity. The ball would move forward with the same momentum, but its velocity would be greater than the pitcher’s, because it is so much lighter. It would be nowhere near what it would on the ground, because on earth, the pitch has a lot of time to generate power from his legs, which would not be possible without something to push on – it would be a very weak throw compared to earth. Your direction would be consistent, so you could develop accuracy, but that would take a lot of time, because the motion imparted to your body and the inability to brace against a solid surface would fuck up the aiming point and the timing of your release.