The New England Patriots entered the draft with needs at cornerback, offensive line, and defensive tackle. They also needed to fill in depth at linebacker. Beyond those four spots, the Patriots were just looking to strengthen their roster as much as possible.
Consider three of the four needs fulfilled, and the fourth an impossibility to complete.
Prior to the draft, the Patriots didn't have a starting guard on the roster, as Dan Connolly remains unsigned. It's very possible that he won't be back with New England with eight offensive line spots already filled up and guaranteed for the two fourth round picks Tre Jackson and Shaq Mason, and the returning veterans (Nate Solder, Sebastian Vollmer, Marcus Cannon, Cameron Fleming, Ryan Wendell, Bryan Stork).
The Patriots double dipped at a strong position and likely have their starting interior offensive line set up for the next five years, with Mason, Stork, and Jackson. There was a mild roar of outrage after the second round when the Patriots let A.J. Cann slip through their fingers, but the Patriots were clearly targeting Jackson in the middle of the fourth- and Shaq Mason offers some of the best upside in the draft.
At linebacker, the Patriots had Jerod Mayo, Dont'a Hightower, and Jamie Collins as starters, but there was little depth behind them. This draft provided three players that could provide depth, along with an undrafted free agent. Geneo Grissom, Matthew Wells, and Xzavier Dickson can all line up at linebacker in different capacities, and UDFA Brandon King is a linebacker/safety tweener that will be interesting to watch. The battle for linebacker depth this season will be much higher quality than last year, which bodes well.
While Vince Wilfork might be suiting up for a different team next year, the head count on the defensive line will be consistent with the addition of first round pick Malcom Brown. Brown offers slightly less athleticism than Wilfork, but is already a polished run defender, with some ability as a pass rusher. The Patriots have to be excited about adding a player like Brown to their defense to compensate for their secondary.
The Patriots didn't take a cornerback to counter the subtractions of Darrelle Revis and Brandon Browner. Instead, they took a safety in the second round in Jordan Richards. He was overdrafted and it's clear that Bill Belichick reaaaaally wants this type of player to work out, and it's easy to see why.
Richards, like Tavon Wilson, has the ability to line up in the slot as a cornerback, stand in the box as a strong safety, and drop back in the deep field as a free safety. Wilson saw a lot of time as a rookie, but repeated mistakes and never recovered. Richards is lauded for his mental ability, so he has a real chance.
One goal with this type of player is to allow three linebackers to stay on the field, which is a clear strength for the Patriots. New England can play cover two with Richards and Devin McCourty as the deep safeties, or they can play cover one and slide Richards up in the slot, with McCourty as the single deep safety. This versatility would allow the Patriots to not have to substitute Pat Chung and Duron Harmon based upon rushing or passing downs.
This still ignores the need at cornerback. The Patriots would have loved to take a cornerback who would be an improvement over Logan Ryan, Malcolm Butler, or Bradley Fletcher, the presumable starting outside cornerbacks.
This doesn't really align with reality, though. The four corners that were likely starting candidates (Trae Waynes, Kevin Johnson, Marcus Peters, Byron Jones) were all taken before the Patriots selected at 32. The others (Jalen Collins, Eric Rowe, Ronald Darby) went in the top 50, and each has a major flaw that made Malcom Brown a more enticing candidate in the opening round.
Beyond the top four, and maybe Rowe, it's a fairly simple argument to make that the players on the Patriots roster are better than what was in the draft. There's no need to take a cornerback just for the sake of saying they took one. If you would take Alfonzo Dennard over the projected growth of these prospects, then why not just move forward with the players on hand?
The Patriots weren't in the draft position to take a cornerback, and it seems likely that once Byron Jones went off the board to the Cowboys, the trade with the Texans for 32nd overall picked up steam.
New England filled the roster with top prospects, when possible, or otherwise picked up quality athletes to compete for depth roles. The secondary never really had a chance to improve through the draft, and it's why the Patriots invested so heavily in their defensive front.
Either they filled the need directly (OL, LB, DT), or they found a way to reduce the need by another means (defensive front to protect the secondary). Yes, there was a clear reach in the second round. But as a whole, this was a successful draft for the Patriots, a team that became much stronger than they were before the draft.