FOXBOROUGH, Mass. -- This will be a process, as it always is. Very little is decided after four days of training camp.

But for those curious of some New England Patriots first impressions, there's only one place to start -- the defense.

We entered training camp with the thought that the team's evolving D was the key to the team's Super Bowl hopes. The first four practices have reinforced that line of thinking. Assuming relatively good health, it's fair to say this defense has the chance to be one of Bill Belichick's best, and it starts at the cornerback position.

Darrelle Revis picked off two Tom Brady passes on Saturday. Barry Chin/The Boston Globe/Getty Images

Darrelle Revis (5-foot-11, 198 pounds) and Brandon Browner (6-4, 221) have been creating havoc for quarterback Tom Brady, who has been frustrated at times, such as Saturday when he had two passes intended for receiver Julian Edelman intercepted by Revis.

Specific to Revis, one of the things that stands out is how he's seldom in bad position. Belichick has already noted his instincts (comparing him to Rodney Harrison in that area), as there have been times when Revis is breaking on a route before the receiver has done so. At the line of scrimmage, his punch has jarred receivers. His footwork is especially fluid with little wasted movement. His ball skills are obviously solid, too.

In the words of Belichick, I'd say Revis "is similar but different" to when we watched receiver Randy Moss in 2007 training camp. It just looks different -- everything is on a much higher level than you're used to seeing.

Meanwhile, Browner has brought a Harrison-type physical presence to the practice field. On Sunday, he de-cleated rookie running back James White in an 11-on-11 running drill, White landing on his backside as the crowd of 13,000-plus roared along with Browner himself. Longtime Patriots followers might recall how Harrison was buzzing around the field in his first training camp with the team in 2003, his hard-hitting style right on the line between the desired edge/intensity and putting valuable teammates in the cross hairs of friendly fire. That's what we've seen from Browner, who if teamed with Revis could help transform a Patriots' D which ranked 26th in the NFL on third down last season.

So these are some first impressions, passed along with a cautious touch.

We want to relay what we see, while at the time, keeping things in the appropriate context. After all, it has been only four practices.