FLOWERY BRANCH — In Thomas DeCoud's locker is a shiny gold belt, akin to something a heavyweight boxing champion might wear. The Atlanta Falcons pass it around each week to the defensive back who does the best job in a series of ball-catching drills.

From the next locker, Dunta Robinson eyes the gaudy prize.

"Thomas gets to brag for a week," the cornerback said. "Next Tuesday, it won't be in his locker. I haven't won it yet, but that's soon to come."

Even though it's all in good fun, the belt does symbolize what the Atlanta defense hopes to become.

The best.

Usually one of the league's lowest-ranked units, the Falcons have spent the past couple of years trying to upgrade their speed and athleticism on that side of the ball. Those efforts are clearly paying off.

Atlanta (3-1) has allowed just 15 points a game, which ranks sixth in the NFL. The Falcons haven't finished that low since their 1998 Super Bowl team gave up the fourth fewest.

They also have taken a huge chunk off their passing yards, which was just what they had in mind landing Robinson as their major free-agent acquisition of the offseason. He's holding down one side of the field, while 5-foot-9 Brent Grimes, who went undrafted out of Division II and spent time in NFL Europa, has shown he belongs in the big time at the other corner.

"We've got the right group of guys," first-round pick Sean Weatherspoon said. "You can just feel it. Nobody resents anyone on this defense. Even me, being a rookie, when I say, 'Come on, guys, let's go,' no one looks at me and says, 'Hush up, rookie.' You definitely can sense that we mesh well together."

Indeed, the Falcons have an intriguing mix on defense. Linebacker Mike Peterson and end John Abraham have each been around more than a decade. Players such as Robinson, safety Erik Coleman and tackle Jonathan Babineux are right in their primes. The last two drafts have produced Weatherspoon and 2009 top pick Peria Jerry, who starts at tackle.

But the guys to really keep an eye on are in their third years: Grimes, DeCoud at safety, end Kroy Biermann and middle linebacker Curtis Lofton, who has quickly established himself as the leader of the defense even though others have been around much longer.

"When guys are hitting that third and fourth year, that's when they start to become the players they're supposed to be," tight end Tony Gonzalez said. "If you can't figure it out by year three or four, more than likely you're not going to figure it out. These guys are starting to figure it out. They realize how good they can be."

Granted, the Falcons have benefited the first quarter of the season by playing offensively- challenged teams such as Arizona and San Francisco. They also caught a break in Week 1 against the Pittsburgh Steelers, who didn't have suspended quarterback Ben Roethlisberger.

But considering where Atlanta has been mired much of its history, no one's quibbling about the improvement shown so far.

Over the past decade, the Falcons have never finished higher than 14th in yards allowed, and they've generally placed in the bottom third of the league rankings. Last year, Atlanta was 21st in total defense, largely because only four teams gave up more yards through the air.

That's why the Falcons gave Robinson, one of the league's better lockdown cornerbacks, a six-year contract that included about $22.5 million in guaranteed money. Robinson has yet to make an interception, which isn't surprising — teams rarely throw his way.

But everyone else has gotten chances. Second-year safety William Moore leads the teams with two interceptions. Grimes and DeCoud each have one, as do Lofton and Peterson. Overall, the Falcons lead the NFL with eight picks.

"It's a combination of experience and chemistry," DeCoud said. "We know our system now. We've played with each other a couple of years now. It's time to cut loose and go make plays. We're showing that with our ability to get the ball back for the offense and stopping the run like we have."

Coming in, everyone knew defense was the key to Atlanta's season.

Quarterback Matt Ryan leads an offense that is loaded with weapons, including Gonzalez, running back Michael Turner and receiver Roddy White. So it's no surprise to see the Falcons ranked among the top 10 in passing, rushing and total yards.

"We understand that our offense is a high-powered, really good offense," DeCoud said. "We felt like we needed to do everything we could on the defense to carry our weight and not necessarily be a weakness."

For now, they'll make do with that gold belt.

But if this keeps up, they all may get a prize at the end of the season.

"We're climbing that ladder to be the best, and that process is lovely," said Peterson, a 12-year veteran, breaking into a big smile. "I'm chasing that ring, man. I know my clock is ticking."