If there's going to be one positional group to define the Patriots 2015 season, it will be the defensive linemen. The offense will be expected to function at it's usual high level, as will the team's linebackers. But it's going to be up to the defensive line to pick up for any extra slack that the secondary will require.
Three of the Patriots past four first picks have been on defensive linemen and these players will have to step up and emerge for New England to experience any long term success.
Defensive Tackle: Dominique Easley, Malcom Brown, Sealver Siliga
Edge Defender: Chandler Jones, Rob Ninkovich, Jabaal Sheard, Geneo Grissom, Trey Flowers
The Patriots will house between eight and ten defensive linemen over the course of the season, and these eight are as close to locks as you can get. These players effectively lock New England into a 4-3 front, as both Jones and Sheard are much better players on the line than back in space. Additionally, Easley and Brown pair to form an ideal defensive tackle tandem.
These players are all either top draft picks, or recently on the receiving end of a new contract. They're not going anywhere.
Defensive Tackle: Alan Branch, Chris Jones, Joe Vellano, Zach Moore
Branch could very well be in the roster locks section as he just restructured his contract, but I believe if a player like Chris Jones or Zach Moore elevates his play in camp, Belichick could favor the youth and potential. Also, Branch signed before Malcom Brown fell to 32nd overall. Plans could have very well changed.
That said, if any of the bubble players make the roster, it will help explain the roster make-up. Jones and Moore most similarly align with Easley's skill sets, and would imply a heavy focus on the 4-3. A player like Branch or Vellano would add depth for a multiple 3-4 front.
From a numbers perspective, Easley is alone, while Brown and Siliga are more comparable in size. An inside edge to Jones wouldn't be implausible.
Defensive Tackle: Antonio Johnson, Vince Taylor
Edge Defender: Rufus Johnson, Xzavier Dickson
All four of these players face an uphill climb to make the roster, even if their chances are non-zero. The edge defender position is just so crammed there won't be any space for others to make the team, while the defensive tackle competition features bubble players with game experience for the Patriots.