Posted by ESPN.com's Mike Sando
The move seemed a little curious because the NFL had awarded San Francisco a two-week roster exemption for Crabtree. Why activate him now? Why not wait until Monday of next week? There would seemingly be no advantage to using a roster spot prematurely.
But there is an advantage in this case.
Leaving open a roster spot would have forced the 49ers to release receiver Dominique Zeigler from their practice squad.
What? How could that be? Here is how: This is Zeigler's third season on the practice squad. Any player spending a third season on a practice squad can do so only if his team keeps 53 players on its active roster at all times.
Releasing Rossum without filling the 53rd roster spot would have affected Zeigler's eligibility.
Another teaching moment here on the NFC West blog.