Just saw these charts on Baseball Savant. I'll post links to the images of base hits allowed to drop by Heyward vs Kemp.
Heyward:
Kemp:
You can easily see just how many hits Kemp allowed to fall in the Easy, Routine, and Tough ranges compared to an elite defender like Heyward. These charts do a wonderful job of illustrating how Kemp costs a team 20+ runs on defense when he lets all those fly balls drop. Many of those become extra-base hits and cause considerable damage.
Heyward:

Kemp:

You can easily see just how many hits Kemp allowed to fall in the Easy, Routine, and Tough ranges compared to an elite defender like Heyward. These charts do a wonderful job of illustrating how Kemp costs a team 20+ runs on defense when he lets all those fly balls drop. Many of those become extra-base hits and cause considerable damage.