I guess I measure it by my height -- anybody shorter than 6'3" qualifies as a small reciever to me. I can't see even someone like Corey Bradford, at 6'0" 200 lbs being able to be a force blocking when it comes to the running game. If I were Texans GM (thank god I'm not) players who were unable or unwilling to take out LB's like Keshawn Johnson would only be considered for 'slot reciever' roles, or as WR's in 3 or more WR sets. I have an incredible antapathy for recievers like Joey Galloway or Terry Glenn. On my (1 and 15) team they'd be 3'rd down guys. I guess for teams like the Texans, who figure to rush more between the tackles than outside, blocking on the ends isn't quite so important, but I can't help but judge themthrough my perspective.
As it stand right now, I would guess the best RB or LB (remember, they're running a 3-4 and still need some LBs) available, unless someone just absolutely slides in this draft (very possible).
It's better to be shorter when it comes to run blocking. Also, at 200 pounds, he will most likely out weigh his CB by 10-15 lbs.