In my view, some commentators are lazily pointing to the Dominique Easley pick and decrying it as too risky on the basis of his ACL injuries. Somehow we are conveniently forgetting the incredibly common nature of ACL ruptures in the NFL these days, and we are still stuck in the old days in terms of our expectations for a player's effectiveness once he's back on the field. We don't have to go over again the recent examples of players dominating less than a year after tearing their ACLs (hello, Adrian Peterson). In my mind, Easley's being an undersized defensive tackle is more risky simply than the fact that he's had two ACL reconstructions. From what I've gathered, Easley should be healthy enough for the beginning of the season. If Belichick thinks he can contribute, there's no doubt in my mind that he'll be in the field for week 1.
The reason this pick has so much potential to help out the team is that it solves much of what was missing in the Pats' defense. With the improvement in the secondary (just take Revis alone), what were the major misgivings about this defense going into the draft? I'd say interior pressure, defensive end depth, and linebacker depth. Easley's potential and his flexibility are huge here.
For one, you now have the possibility of pairing a quick, penetrating, smaller defensive tackle with a stouter nose tackle type, something that the team has been looking for for some time. Never mind Wilfork for the time being; everything I understand about Achilles' tendon injuries (apparently much more somber in terms of a player coming back to full capacity than ACL injuries) suggests that whatever we get from him this year is gravy. The same might be said for Tommy Kelly, who's also coming back from injury. In my opinion, what you got from Sealver Siliga last year was a revelation. He wasn't much of a penetrator, but that's not what the Patriots asked of him. He was absolutely huge in turning around the Pats' run defense late in the year. Pair Siliga (along with whatever you get from Wilfork, Kelly, and Joe Vellano) with Easley (and behind him Chris Jones, who showed some encouraging ability to rush last year but was miscast as a run-stuffer), and you finally have some important balance at the DT spot.
As for the other two defensive needs... There's a possibility that the Pats play Easley some at defensive end rather than tackle, since he experienced playing all over the line in college. But even if he stays in the middle, Easley takes some pressure off of Chandler Jones, who was asked at points last year to slide inside to tackle on obvious passing downs. And if another defensive end emerges (like Buchanan or Will Smith or Zach Moore), then that conceivably opens up space for Nincovich to play some linebacker if needed.
The point is, by adding talent in the form of Easley, the Pats plug a hole at defensive tackle that can have a huge trickle down effect to other parts of the defense. The question, then, is all about the knees, and like I wrote above, my particular take is that the message in the media thus far on this has been to exaggerate the level of injury risk.