NFLDraftCountdown put out a list today of their 'Super Sleeper Team,' with Will Campbell as one of two DT selected.
They seem to be struggling with what exactly a 'sleeper' is these days, but this is a good indicator of what they think means:
None of these guys were invited to the Scouting Combine and, honestly, most of them will go undrafted. However, they are all prospects who I like and feel have the potential to make a NFL roster and contribute.
They also list previous members of their 'sleeper' lists that have had impacts in the league:
Eric Foster (Colts), Brian Witherspoon (Jaguars), Mike Cox (Chiefs), Brett Kern (Broncos), Steven Hauschka (Ravens), Mackenzy Bernadeau (Panthers), Aaron Brown (Lions), Ryan Succop (Chiefs), Nick Reed (Seahawks), Larry Hart (Jaguars), Deji Karim (Jaguars), Reggie Stephens (Bengals), Jorrick Calvin (Eagles), Joe Webb (Vikings), Sam Shields (Packers), Daniel Kilgore (49ers) and David Carter (Cardinals). Last year's team had Mike Harris (Chagers), Gino Gradkowski (Ravens) and Greg Zuerlein (Rams).