Interior DL depth in spotlight

First-year defensive lineman Armond Armstead underwent surgery for an infection and is in good condition and expected to make a full recovery, the Patriots announced Monday night. A timetable for Armstead's return has not been determined, according to the team.

Armstead projected to a top backup role behind starters Vince Wilfork (6-2, 325) and Tommy Kelly (6-6, 310), but instead opened training camp on the non-football illness list.

This further thins the team's depth, especially after 2012 co-starters Brandon Deaderick and Kyle Love were released in the offseason.

Here is a look at the remaining players on the interior defensive line depth chart, with some quick-hit thoughts:

Marcus Forston (6-3, 305) -- Spent most of last season on the practice squad and is the player currently on the 90-man roster who seems most affected by Armstead's absence. He has been the top backup behind Wilfork and Kelly and showed up on the kickoff return unit in the wedge, which reflects in part how he moves well for a player his size.

Joe Vellano (6-2, 300) -- The rookie free agent from Maryland caught our eye in Monday night's in-stadium practice with some short-area quickness in rush drills. On one rush, he was competitive with center Ryan Wendell, which reflected that he wasn't just having success against rookie/developmental interior linemen. From a size perspective, he's the lighest of the team's interior linemen.

Cory Grissom (6-2, 316) -- Rookie free agent from South Florida has yet to practice and the Boston Herald reported that a concussion is the reason. After the draft, NFL.com analyst Gil Brandt rated Grissom as one of the top undrafted linemen.

Anthony Rashad White (6-2, 330) -- A stockier, bigger lineman, he showed some power in his bull rush Monday night. He signed with the Patriots in the days leading up to training camp, so he's had some catch-up work to do in the program.

QUICK-HIT THOUGHTS: If this was the early years of Bill Belichick's coaching tenure, and the Patriots were running the 3-4 defense that had a nose tackle and two 5-technique ends, the depth of this position would be more of a concern. But the role of the "big" defensive lineman is different in the team's defense these days; the club now lines up with two of them in the middle and the third and fourth linemen on the field are hybrid end/outside linebackers (Rob Ninkovich/Chandler Jones). At this point, Forston and Vellano are viewed as the leading candidates for backup roster spots along the interior defensive line, with no guarantee that the Patriots would keep two backups. On Sirius XM NFL Radio, Bill Belichick said, "It’s a position that in the past we’ve had a lot of guys that aren’t real high draft choices play a lot of football for us."