Even more urgent than our 40 man, I'm pretty sure we can't game the active MLB roster in September anymore. According to wikipedia, we get 2 more slots. Those slots should go to some combination of Pearson (if his arm doesn't fall off), Biggio, and Jansen. Merryweather too if he's still alive.
As much as we don't like Jansen, he needs to be up if he finishes rehab. Having a good glove backup C will free up Kirk to hit more than once a week. Every single one of these players is more valuable to us than Mallex Smith.