FOXBOROUGH, Mass. -- The first thought that came to mind with the Patriots' two trades on Tuesday -- acquiring defensive linemen Ben Bass (Cowboys) and Jerel Worthy (Packers) -- was that Bill Belichick is being proactive to avoid another repeat of 2013 when a run of injuries left the team thin at the heart of its defense.

By the fifth week of last season, the Patriots had lost the top three defensive tackles on their depth chart -- Vince Wilfork (ruptured Achilles, Sept. 29), Tommy Kelly (torn ACL, Oct. 5) and Armond Amstead (infection in July, season-ending IR). That left them to scour the waiver wire for Sealver Siliga, while also thrusting undrafted free agent Joe Vellano and prior waiver-wire pickup Chris Jones into top roles.

It's almost as if Belichick is saying, "We made it work last year against long odds, but let's cover ourselves a little bit better this time around just in case."

Bass and/or Worthy might not even make the Patriots' roster. But after Siliga injured his left hand last Tuesday (he was in a cast) and could miss extended time, and Jones injured his left ankle in Thursday's preseason opener and is likely to miss the rest of the preseason, the depth is being tested once again and the idea of bringing a few more big bodies into the mix makes sense.

Maybe something sticks.

On Tuesday, the Patriots lined up with veterans Tommy Kelly and Vince Wilfork alongside Vellano at defensive tackle.

The other defensive tackles taking part in 11-on-11 drills were Eathyn Manumaleuna, L.T. Tuipulotu, Marcus Forston, Zach Moore and Will Smith. Of the group, Moore and Smith are more natural ends.

A boost will come once first-round draft choice Dominique Easley progresses to participating in full-team drills. But he's not there yet, and so for now players like Bass and Worthy fit the bill as depth-based options who could help the team in the event there is a repeat of the run of injuries that unfolded in 2013.