You can't say that the Patriots aren't looking under every rock in order to strengthen their secondary. New England currently has a host of #2 cornerbacks on the roster in Logan Ryan, Alfonzo Dennard, Malcolm Butler, Kyle Arrington, Bradley Fletcher, and Robert McClain, but the door is still wide open for a top level cornerback to join the roster.
The make-up of the depth chart looks very similar to 2010, when the Patriots selected Devin McCourty despite heavy investment in the position in recent drafts. Terrence Wheatley (2008 2nd), Jonathan Wilhite (2008 4th), Darius Butler (2009 2nd), and Leigh Bodden (received a 3-year extension in 2010) couldn't stand in the way of improving the roster and it's because the coaching staff didn't have much trust in Wheatley or Wilhite.
It could be argued that Dennard and Ryan could be in a similar boat, as Dennard was benched during the middle of the season and Ryan wasn't able to offer a level of consistency in his second season. It's very possible the team is high on Butler, and that they believe one of Fletcher or McClain could solidify the secondary, but the position's depth isn't strong enough to deter adding another top level prospect.
And there are no prospects currently off-limits.
New England has had workouts or interviews with top round prospects like Wake Forest's Kevin Johnson, Connecticut's Byron Jones, Washington's Marcus Peters, and Utah's Eric Rowe.
They've had top coaches and personnel people attend the Pro Days of other Day 1 or Day 2 players like Michigan State's Trae Waynes, Louisiana State's Jalen Collins, Florida State's Ronald Darby and P.J. Williams, Florida Atlantic's D'Joun Smith, Southern California's Josh Shaw (Mike Lombardi was on hand for this visit), and Ohio State's Doran Grant.
The only top tier prospect that hasn't been linked to the Patriots by a visit or a Pro Day is Miami (OH)'s Quinten Rollins, the reigning MAC Defensive Player of the Year in his only year of college football. Rollins was a basketball player prior to 2014.
There are some mid-round prospects that have sparked interest, too, with Bill Belichick attending the Pro Days of Louisville's Charles Gaines and Central Florida's Jacoby Glenn. The Patriots also had personnel at the Pro Days of Texas Christian's Kevin White and Stanford's Alex Carter.
Outside of the top prospects, the Patriots have been linked to potential free agent prospects like Tennesee's Justin Coleman, Western Kentucky's Cam Thomas, Utah's Davion Orphey, Fresno State's Curtis Riley, Maine's Axel Ofori, Texas Southern's Tray Walker, and Memphis' Bobby McCain. Most of these players have fantastic three cone times and look to be developmental prospects and likely practice squad or special teams candidates.
The Patriots have also had cornerback coach Josh Boyer work out, and have a planned visit with, Southern Florida's Chris Dunkley. Dunkley is a former wide receiver, but converted to cornerback his senior season. He was suspended in 2012 for domestic violence and it's likely the Patriots are just performing their due diligence.
This isn't a fully comprehensive list of visits, but it shows that the Patriots are showing interest in adding bodies to their secondary. When the draft passes, don't be surprised if one or two of these names end up in New England.