Aging is a part of baseball.
Hell, it's a part of life.
There soon comes a time when a ball player has to admit that he just doesn't have it anymore, or he simply can't compete at the same level he used to.
Some players try to hold on for dear life, switching positions, switching from starting pitcher to reliever, anything.
Others know when it's time, and bow out respectably.
And some simply get forced out of the game due to rampant injuries.
Here are the top 20 superstars whose bodies may let them down in 2011.