The Patriots allowed the 2nd most passing TDs in the NFL last year, and the 2nd most 40+ yard pass plays. This off-season, there's been a concerted effort to improve the pass defending elements of the defensive alignment.
Last week they acquired veteran Shawn Springs, and today they signed Leigh Bodden formerly of the Detroit Lions.
Neither of these guys are shutdown corners, neither of these guys are big playmakers, but neither of these guys are Deltha O'Neal. Springs is a 13 year old veteran, and Bodden has 7 years in the League. They don't make big mistakes. They don't blow coverage schemes. They'll help the younger CBs, like Terrence Wheatley, develop into solid CBs.
But once again this year, the quality of the pass-defense will be determined by the consistency of the pass rush. Pass rushing isn't just about sacks, it's about forcing hurried throws, and not allowing the QB to go through his progressions. The front 7 will determine how many passing TDs and 40+ yard passes the defense allows, more so than the DBs.