FOXBOROUGH, Mass. -- When Baltimore Ravens coach John Harbaugh looks at the New England Patriots' defense, he sees what he always has.
"It's the fundamental soundness that they've always had and the multiple looks they can give you," Harbaugh said Wednesday as his team began preparations to face the Patriots on Sunday at Gillette Stadium. "It's the fact that from one week to the next they can reinvent themselves, and the fact they have been able to plug in personnel. I have so much respect for that."
The defense, which has been without 2008 leading tackler Jerod Mayo (sprained MCL) since the second drive of the season and has absorbed other injuries such as defensive tackle Vince Wilfork (ankle) and cornerback Jonathan Wilhite (groin), has been a pleasant early-season surprise.
Shaky at times, having produced only three turnovers, and unable to produce consistent pressure on opposing quarterbacks, it has still produced some solid bottom-line results, holding the Buffalo Bills to 17 points, the New York Jets to 16 and the Atlanta Falcons to 10.
So how has the defense done it?
"The biggest thing they've done so far is not allowing a lot of plays to be run by the offenses, and that's a credit to both their defense and their offense," opined Ravens quarterback Joe Flacco, adding that the Patriots are a sound run-stopping team that also eliminates the big play in the passing game.
Flacco's analysis, like many of his passes this season, is on the mark.
The Patriots' defense has been on the field for just 148 plays, the second fewest in the NFL behind only the Giants (144). New England has had a time of possession edge of 35:56-24:04, the second highest disparity in the league.
Better third-down defense, along with help from its own clock-grinding offense, has been a winning combination.
One of the most impressive aspects of the Patriots' defensive performance has been competitive play against the run despite employing a sub package. Usually when an extra defensive back is added in place of a linebacker, it lightens the box and invites opponents to run.
But the Patriots, who have been in a sub package 56 percent of the time this season, have struck a nice balance.
Other than some struggles against Bills running back Fred Jackson in the opener, they've created enough resistance up front against the Jets and Falcons -- two strong running teams -- while helping themselves in the back end of the field with an extra defensive back.
Safety Brandon McGowan has been a key.
The 5-foot-11, 210-pound hard-hitter has played a hybrid role in which he's dropped into the box to support against the run almost as a linebacker, while other times staying in the deeper parts of the field as a pure safety during passing situations. He earned a game ball for his effort Sunday in which he created a Michael Turner fumble and helped limit dangerous tight end Tony Gonzalez to just one catch.
The Patriots employed a three-headed safety approach last season with Rodney Harrison, James Sanders and Brandon Meriweather. McGowan, in his first season with the club after four with the Bears, has filled in for Harrison this season while cutting into Sanders' playing time.
Overall, one of the defining characteristics of the Patriots' defense under Bill Belichick has been the ability to take away what an opponent does best.
In the opener against the Bills, it was the big-play threat of receivers Lee Evans and Terrell Owens. Against the Jets, the run game seemed to be the primary focus, while Gonzalez was the main target against the Falcons.
Each time, the defense has risen to the task, giving the Patriots a chance to win.
While the true test figures to come when they are on the field for an extended stretch of time, the performance has been an unexpected surprise through the season's first three games.
Mike Reiss is the Patriots blogger for ESPNBoston.com. You can reach Mike by leaving a message in his mailbag.