He's probably a sleeper.
you should definitely take him, but if he's rated very low then he won't be on the radar of a lot of teams. I've never seen him, so I can't tell you where he gets picked.
If he's rated really low, you could probably get him in the 4th-7th rounds. Which would be a steal. No point in signing him in the 1st round if no one else wants him that high. So you're better off signing someone else, and waiting to pick him, or trading down and picking him later, so you will get him for cheap.
I use the pick the pick method. As soon as I start to see him on some peoples lists, then I start thinking about trading up to get him.
I think it's always better to get a guy in the 3rd and 4th round because you can usually get them for extended years, for cheap. If you sign a guy in the 1st round you pay a lot for him. If you sign him in the 7th round, or if he doesn't get drafted at all, then you usually only get a contract for 1 year. Then you'll have to pay him more in the second year, after he realizes how good he is.
However, I almost always draft other guys that I want in those rounds that aren't going to fall much further, knowing I can still get that sleeper later on. I just end up resigning them if I like them. So far I haven't had salary cap issues yet.