Atlanta gave up only a field goal while Miami starting quarterback Chad Henne was in the game and beat the Dolphins 16-6 on Friday night.
Middle linebacker Curtis Lofton led the Falcons' defensive charge with 11 tackles, two for losses. Erik Coleman intercepted a pass in the end zone, and the Dolphins converted only one of nine third- and fourth-down situations with Henne, who played one series into the third quarter.
"Our defense played well," Smith said. "We were getting off the field, and you've got to do that to limit your exposure on defense."
Lawrence Sidbury had a sack, two quarterback hits and a tackle for a loss. The Falcons (2-1) are hoping for defensive improvement after ranking 23rd in the NFL last year in yards allowed per play despite a 9-7 record.
"We wanted to come out and set a tone, and we did a good job of that," Lofton said. "We've got two weeks left to do some fine-tuning. It's like a car -- you've got to keep fine-tuning it so it will run pretty."
Atlanta's Matt Ryan threw his first touchdown pass of the exhibition season. He led scoring drives of 60 and 54 yards, the second of which took more than seven minutes.
Ryan played one series into the third quarter and finished 13 of 26 for 103 yards, with one interception. He helped the Falcons convert eight of 14 third-down situations against Miami (2-1).
"I liked what I saw tonight from all three phases," Smith said. "We played effectively and with a lot of energy."
Michael Turner was a workhorse for Atlanta in the first half, rushing 47 yards in 16 carries. He lost a fumble.
Henne went 10 of 22 for 123 yards with one interception, and at least three of his passes were dropped.
"We weren't efficient," Henne said. "Overall it was sloppy. We really need to get better. Time is running out for us."
Henne and Brandon Marshall hooked up for completions of 26 and 20 yards in the final 45 seconds of the first half, giving the Dolphins a first down at the 7. But linebacker Mike Peterson tipped a second-down pass, and Coleman intercepted it in the end zone.
"Mike Peterson did a great job of getting back in coverage and getting a hand on the ball," Coleman said. "When it went up in the air, I had to have it."
"They were better than we were up front physically," Dolphins coach Tony Sparano said. "We played sloppy, inconsistent -- at times did some decent things, but couldn't finish. There was something always unexecuted."
The Falcons converted three third-down situations on their second possession before Ryan hit Roddy White for an 18-yard score. White later beat Sean Smith on a deep route, but Ryan overthrew him near the goal line.
Smith did not start because he violated a team rule, Sparano said.
Dolphins backup Chad Pennington went 7 of 14 for 62 yards and led them to a field goal.
Atlanta's first-teamers had two turnovers, both in the first half. Cornerback Vontae Davis forced Turner's fumble, and Dolphins newcomer Karlos Dansby recovered, while Ryan was intercepted by Yeremiah Bell.
Davis made seven tackles, one for a loss, and three passes defended.
Cornerback Dunta Robinson, the Falcons' major offseason acquisition, did not play because of a lingering hamstring injury. Defensive tackle Peria Jerry, the 2008 first-round draft pick who missed most of his rookie season with a knee injury, made his 2010 debut and had a quarterback hit.
Trent Williams, who left Sunday's game against Carolina and who did not practice on Wednesday, said he'll be ready for the Giants.
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