MIAMI — The Atlanta Falcons' new investment in Devonta Freeman is already reaping dividends.

Now the NFL's highest-paid running back, Freeman looked the part in a brief appearance Thursday night, scoring on a 15-yard reception from Matt Ryan as Atlanta lost to the Miami Dolphins 23-20.

Freeman, who agreed Wednesday to a $41.25 million, five-year contract extension, scored to cap the Falcons' first preseason possession.

"It was just about me competing, doing what I love to do," he said.

Freeman ranked seventh in the league last year with 1,541 total yards.

"We're really thrilled to get this deal gone, knowing what a significant factor he is for us," coach Dan Quinn said.

Freeman's touchdown capped a 36-yard drive by new offensive co-ordinator Steve Sarkasian's unit after a 39-yard punt return by newcomer Andre Roberts.

The Dolphins' exhibition season began badly. Second-round draft pick Raekwon McMillan, the front-runner to start at middle linebacker, hurt his right knee on Roberts' return.

After the game, coach Adam Gase said he did not yet know the severity of the injury. McMillan left the locker room on crutches.

"It's tough to see a young player go down," Gase said.

Miami backup safety Walt Aikens also left the game in the first quarter with a back injury.

The Falcons, who blew a 28-3 advantage against New England in last season's Super Bowl, this time let a 20-10 fourth-quarter lead get away. Undrafted rookie Damore'ea Stringfellow caught a 99-yard touchdown pass from David Fales to cap Miami's comeback, but neither is likely to make the roster.

First-teamers on both sides saw little or no action. New Miami quarterback Jay Cutler sat out, and backup Matt Moore played one series, which went three-and-out after confusion forced the Dolphins to call timeout before their first snap.

"That was my fault," Gase said with a wry smile. "I thought they were in different personnel and changed the call, and didn't give Matt enough time."

The Falcons were on their third quarterback before the first quarter ended. Ryan played one series and went 3 for 3, hitting three receivers for 32 yards.

His touchdown pass came on fourth and 1, when he faked a handoff to Freeman, who then circled out of the backfield to make the catch in the flat and score untouched.

Freeman and Ryan celebrated in the end zone with a flying shoulder bump and hug.

Miami's second-team offence drove 40 yards to the Falcons' 20 before Atlanta's first-teamers came out of the game. The Dolphins then settled for a field goal.

CROWD SUPPORT

Freeman, who grew up in Miami, said he had about 70 kids from his local youth program at the game, along with two dozen friends and relatives.

"It's always fun to come back to Miami," he said.

GOOD CATCHES

Dolphins receiver Leonte Carroo, a disappointment as a rookie last year, outmanoeuvred C.J. Goodwin to catch a 33-yard touchdown pass from Brandon Doughty.

"We were on the same page, and I was able to make a great play on the ball," Carroo said.

Stringfellow hauled in Fales' pass at the Miami 30, cut twice to elude safety Marcelis Branch and raced down the sideline for his score to put Miami ahead to stay.

KICKING CONTROVERSY?

Matt Bryant, who's entering his 16th season, missed a 47-yard field goal attempt for Atlanta, while second-year pro Mike Meyer made kicks of 30 and 53 yards.

"Mike nailed it like he does in practice," Quinn said. "He has a fantastic model to look for in terms of consistency in Matt Bryant."

GROUND GAME

Terron Ward, contending to be Atlanta's third running back, carried 11 times for 48 yards and a touchdown. Kenyan Drake led Miami rushers with 21 yards in five carries.

YOUNGSTERS

Rookie defensive tackle Davon Godchaux and second-year receiver Jakeem Grant had impressive moments for Miami.

"I liked how all of our young guys tried to play as fast as they could," Gase said. "And I didn't feel like we had a lot of mistakes."

SIDELINED

Falcons first-round draft pick Takkarist McKinley and receiver Julio Jones sat out. Among those not playing for the Dolphins were running back Jay Ajayi, centre Mike Pouncey and left tackle Laremy Tunsil.

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