This isn't baseball. The Pats are allowed to add a player off the street if they want.
The question is whether or not that person would be able to do anything for the team. Unless its Deion Branch (still with Seattle) , Troy Brown (maybe a couple years off did him good), Reche Caldwell (Is he out of BB's dog house?), David Patten (not sure if he's in the BB doghouse still or not) , or David Givens (still trying to get healthy) , my guess is no.
The one option on the team is Darnell Jenkinis. Who is a small, physical type receiver who is 5'9" and supposedly relies on his quickess and toughness to make plays.. The issue with Jenkins coming out was that he tended to let too many balls get into his body, so he had the dropsies. Another option could be H-Back/TE Rob Myers..
My guess is that Stanback and Edelman get used more at WR during practices and that Watson also gets flanked out more..
NFL Players
Having reviewed that, there are some very interesting names out there. Drew Bennett, Bobby Engram, Robert Ferguson, DJ Hackett, just to name a few. Its a matter of whether they have anything left..