It’s an interesting question and it should be defined based on what exactly you focus on. What is optimal and what is opposite/sub-optimal.
Also, saying “inside to outside”, what do you refer to? Camera angle? Court lines? Incoming ball? Outgoing ball?
For example, if you look at high I/O fade forehand, and use target line as reference, the hand will clearly move from straight to the ball first and then curve inward.
But if you examine a CC FH on the run that a player draws back CC, you will see clean inside-to-outside swing that never turns truly back across until follow-through.
You can also say that if hand is taken to 5 or 6 o’clock back, it will then inevitably travel outward towards the ball first. Absolutely! But that’s, for me personally, not the part of the swing where I perceive if my swing is outward or from the outside: I do pay attention to it on the final stage of the swing, where hand isn’t moving with torso uncoil no more, but accelerates to deliver racquet head properly across the ball.
So again, not arguing right or wrong, but for me this talk is important for how you attack the ball from the slot/lag: you get to slot/lag
somehow in order to have the hand at good spot to attack the ball — either inside-to-outside, or inward.
Hope I put it clear enough to transmit the idea I rely on.
Another layer to it

It’s not just which sidespin the ball gets, not just where the ball is sent. It’s also how exactly you execute:
- More uncoil, shoulder forward, wrist held laid back. Fade-type, but can be hit with low ball to produce more clean topspin/flat shot, pulling the handle up and forward. Think Rublev playing low ball. Or same idea but against high ball: think most chest-high I/O power drives.
- A bit more controlled uncoil, torso “slows down” facing the target, arm takes over. Wrist recovers from full layback towards less extended position. Usually used on lower balls to lift, spin and draw… but can be used on higher balls when hitting side leg loads and drives body up and into the ball, and racquet gets released into the ball. Most Rafa high FHs, including buggy-whip are like this. Produces heavy topspin, but less drive and fade.