It's like when Alex Smith threw that pick against Chicago. Crabtree didn't have the speed to get to the ball so the DB outran him and then picked it off.
By the way, Jerry Rice was said to have no quickness or speed. He ran a slow 40 and teams thought he was slow as fuck. On film he didn't look blazing fast, either. Tell me, who has scored more TDs than him again?
Look I'm not saying Crabtree is a burner or anything like that, but he isn't nearly as slow as you'd like him to be. His game speed is not below that of the defenders he's been matched up against. His speed doesn't stand out either way, good or bad. If you've watched a Niner game at all this season and seen Isaac Bruce on the field, you'd know what slow looks like. Crabtree does NOT look like that. Sorry.