It remains an odd anomaly -- Bill Belichick’s blind spot when it comes to evaluating collegiate prospects.

Over the last decade, the Patriots’ defense had been built, erased and rebuilt again. The franchise has been successful in so many aspects of their team-building process, which has allowed them to have a tremendous run since the early days of the 21st century. At most every position across the board, they have been able to consistently draft and develop the talent needed to keep them at or near the top of the NFL mountain.

But in that same span, Belichick and the Patriots continue to swing and miss with alarming regularity when it comes to drafting defensive backs. In the last decade, they’ve picked up some very good free-agent defensive backs -- both high-profile guys like Rodney Harrison and unheralded guys off the street like Randall Gay. But of the 17 corners or safeties they’ve selected on draft weekend over the last 10 years, they’ve found one player of impact (Asante Samuel) and a few respectable additions (Devin McCourty, Ellis Hobbs and James Sanders). The rest of the list is an eminently forgettable group:

2003: Defensive back Eugene Wilson (second round), cornerback Asante Samuel (fourth round).

2004: Safeties Guss Scott (third round) and Dexter Reid (fourth round).

2005: Cornerback Ellis Hobbs (third round), safety James Sanders (fourth round)

2007: Safety Brandon Meriweather (first round).

2008: Cornerbacks Terrence Wheatley (second round) and Jonathan Wilhite (fourth round).

2009: Safety Patrick Chung (second round) and cornerback Darius Butler (second round).

2010: Cornerback Devin McCourty (first round).

2011: Cornerback Ras-I Dowling (second round) and defensive back Malcolm Williams (seventh round).

2012: Safety Tavon Wilson (second round), safety Nate Ebner (sixth round) and cornerback Alfonzo Dennard (seventh round).

They've taken different paths on the journey from New England draftee to NFL obscurity: Players like Eugene Wilson and Wheatley flashed positively early before dropping off the face of the earth, while others like Scott, Reid, Butler and Wilhite never really found their footing. Hobbs and Sanders had their moments, but in the end, one of 17 has had a sizable lasting impact. It's an astoundingly low mark for a team that has had great success in player development in so many other areas.

So why have so many of New England’s homegrown defensive backs flamed out over the last decade? One school of thought is that Belichick simply utilizes them differently than other teams -- and not in a positive way.

“Most coaches have a defense they like, they install it, and once you learn it, everything looks much better. Bill Belichick doesn’t do that -- he likes to create gameplans, not defensive systems,” said analyst Sam Monson of Pro Football Focus. “As a result, he wants guys who can do a bit of everything so that he can change it week to week and exploit an offense in specific detail. That’s reasonably simple to do with the front seven. You need guys with a specific skill set, but if you’re looking for those guys for long enough, it’s easy to acquire them.

“I’m not sure the same holds for defensive backs, especially young ones,” Monson added. ”Defensive backs are at their most comfortable when they have a system and get that mastered -- then, they can work on the nuances of the coverages and then they start to blossom. I doubt there are many defensive backs in the NFL that would actively enjoy a scheme that could change from man to zone, or off to press coverage from week to week.”

Monson argues that often times, the position is more about instinct than anything, which ultimately hamstrings the Patriots’ young and untested defensive backs.

“Playing defensive back might be the most instinctive position of all, and the more you mess with the program, the tougher it is for them to just play on instinct,” he said. “When that happens, they’re constantly thinking, and thinking time in coverage is yardage.”

While players like Sterling Moore and Kyle Arrington made their bones with the Patriots after starting elsewhere, the Patriots currently have seven homegrown defensive backs on the roster: McCourty, Chung, Wilson, Dowling, Dennard, Ebner and Williams. At this stage, it’s premature to judge the 2012 draft picks: Wilson, Ebner and Dennard are in the nascent stages of their professional careers, and have flashed some good and some bad in their relatively short time in the NFL. In addition, Williams hasn’t seen a significant snap in his brief pro career, having bounced back and forth between the practice squad and active roster.

However, there’s a more of a fully-formed picture of the other three based on their professional experience. Here’s a look at where they’re at:

•The clock is ticking on Dowling, who has taken a precipitous slide down the depth chart since the start of camp. It’s worth noting that the team thought enough of Dowling to have him start the first two games of the 2011 season before he suffered an injured hip and was lost for the season. This summer, he appeared to be in line for a starting job, only to be surpassed by a handful of other corners -- he’s played just 24 snaps since Week One.

•As for Chung, he and Gregory started the season on what certainly appeared to be a positive note, but whether it’s the fact that Gregory has battled injuries over the last three weeks, an injury Chung himself has sustained or miscommunication issues with the rest of the defensive backs, he’s appeared to struggle. (A combination of Chung as the in-the-box safety providing support against the run and Gregory at the free safety spot would be ideal for the Patriots, but Gregory’s hip injury has sidelined him the last two games.) He is in the final year of a four-year deal he signed as a rookie, and stands to lose the most among the entire secondary if he continues on his current pace for the rest of the season. (Think about this: in his three-plus seasons in New England, can you recall a single memorable positive play made by Chung?)

•As for McCourty, it’s not saying much, but the Rutgers product has been the Patriots best and most consistent defensive back over the course of the first six games, and many times this season has flashed the potential to regain the form that got him all the way to the Pro Bowl as a rookie. Patriots coach Bill Belichick said Monday in WEEI that McCourty has had a “good year” and said he’d “improved in a lot of areas.” However, while McCourty does have some positional versatility -- he spent some time at safety at the end of the 2011 regular season and into the playoffs -- don’t expect him to show up at safety anytime soon.

“He hasn’t really worked back there,” Belichick said when asked about the possibility of McCourty at safety this season. “He’s done a really good job of the things we’ve asked him to do. We’ve asked him to change some things and do some things differently and he’s done a good job of that. I think he’s coming along at corner, and that’s where he’s been.”

While critics will openly question the state of the pass defense (especially when contrasted with a very stout run defense that has bottled up top-flight backs like Chris Johnson, Fred Jackson, C.J. Spiller and Marshawn Lynch this season), the Patriots will continue to preach team defense. Defensive lineman Vince Wilfork said Monday that it’s not just the secondary -- when one group slips up, it creates a domino effect that leads to larger defensive breakdowns. 

“You know what? I’m not going to point fingers at anyone because this isn’t track and field where you run 100 meters and get a medal or you throw a shot put and you just get a medal,” Wilfork told WEEI. “This is a team effort, and I would never throw my teammates under the bus. We can do a lot better job of containing the quarterback, being able to get a little more pressure on these guys, so I’m not going to sit here and say it’s all our secondary’s fault, because it’s not. 

“The rush has to match the coverage, and the coverage has to match the rush. At times we do it, at times we don’t, so I think it’s [about] eliminating bad football. Eliminate bad plays. If we just do that, we would be OK. But we have to be able to learn from and we’ve got to be able to move forward. We’ve got to be able to get better. We have to.”