Question

While catching a ball the player lowers his hands

Answer 1

He does so to increase time which decreases the momentum and so he does not need to apply great amount of force which could injure him

Answer 2

While catching a ball player lowers his hand because in this way he increases the time of catch to reduce the momentum of ball to zero. As we knoe Force=Change in momentum/time.
Therefore, player has to apply a smaller force against the ball stop it. The ball in turn exert a smaller force on his hand and thus hands are not injured and he can catch without missing it.