OR if the person you are throwing to cannot cleanly catch and put up the ball in one move.
There are three primary reasons for missed passes:
1) The pass is a good, well-placed feed, but the recipient isn't mentally ready to receive the pass and they're not expecting.
2) The passer simply makes a bad passing decision or an errant pass
3) Hands of stone: The pass is well-placed but the recipient doesn't have soft-hands and has never worked on "gathers"
-One and two are both mental, unless it is a question of bad mechanics... While 3 is purely mechanical.
If the pass is the proper one and the recipient doesn't have their head in the game, A little "time on the pine" can most often take care of this. The drill I would use for this is to put them into a passing ring with two balls. And let the ring, call out "pass" a fraction of a second before sending it, making the recipient have to catch passes from every angle, without having a ton of time to setup for the reception. . . . If it is an errant pass I would make the passer go through some basin passing drills and make sure it was purely a bad decision versus bad mechanics. Another angle I would look at is, "Is there proper communication pre-pass between the passer and recipient. I can do this by watching film and easily decipher what caused the bad connection. . . I teach my girls that the recipient's hand position dictates the pass they want. Hand down = bounce pass,, Hand out = direct pass and finger up = lob. (When the lob is sent to the recipient, it HAS to be as perfectly executed as a taken-shot. The passer has to "shoot" the ball into the held up finger perfectly.
The hands of stone thing is easily cured by letting the player do "gathers". Gathers are a drill where two girls get a good distance apart and may only use one-hand to "both, send the pass and catch the pass... The cradle hand brings the pass into the body area and then the cradled ball is brought into the non-receiving hand in an aggressive clapping motion. The passer will pass to the recipient using a wide variety of angles, methods and speeds, so that the recipient has to learn to bring in lobs, bullets, bounces, etc with one hand.