Chase and Throw Drill
Place three or four balls some distance away from the stumps. The fielder begins facing the stumps. On the call, they turn, sprint, field the ball and return it to the keeper then jog back. Repeat for all the balls then swap with the keeper. Do three sets.
Variations
The fielder/keeper begins in a lying down position.
Use more balls.
Have the ball fed out so it is moving.