How rapidly can one naturally increase strength?

Squawking Baseball addresses the allegation that A-Rod must have been using steroids because of how rapidly he increased his bench press. It's a short read, but hard to quote succinctly, so let me sum it up like this:

1. It is very possible to naturally increase the amount of weight you are lifting very rapidly.
2. It is even more possible when you are as young as A-Rod is alleged to have been when he made his rapid strength gains.
3. It is even more possible when you consider that A-Rod was already outlandishly gifted physically with massive incentives for increased strength.

Yes, I am aware that point three is also an argument that he did use steroids.

It's important to remember that weightlifting was something in which baseball players did not engage for many, many years. Untangling the effects of naturally increasing strength due to weightlifting from the effects of increased strength due to PED usage while weightlifting is nearly impossible.