MIAMI GARDENS, Fla. — Brent Grimes is listed at 5-10 and 190 pounds and looks smaller when surrounded by NFL behemoths, which makes him easy to overlook and underestimate.
Even so, he appears to be a huge steal for the Miami Dolphins.
"They call him Mighty Mouse," teammate Cameron Wake said. "He's a small guy, but he can do amazing things."
The Dolphins acquired the former Atlanta cornerback during their free-agent shopping spree in March, and while the acquisition was overshadowed by their other signings, Grimes has significantly upgraded the secondary.
The unit faces a tough test Sunday when surprising Miami (2-0) plays its home opener against the Falcons (1-1) and Matt Ryan.
"They present a lot of problems," Grimes said. "They've got great weapons with a great quarterback to throw it to them."
Grimes would know. He spent seven years in Atlanta and made the Pro Bowl in 2010. But his market value plummeted after he tore his Achilles tendon in last year's season opener, and he signed a $5.5 million, one-year deal with Miami.
Grimes showed he's fully recovered by making several big plays, including a leaping interception in the end zone against Indianapolis' Reggie Wayne to protect a fourth-quarter lead last week.
"He looks healthy. He looks great out there," Ryan said. "He had a big interception last week. He went up and high-pointed a ball against a really good wide receiver. That's something I've seen too many times out at practice while he was here in Atlanta."
Don't look for Grimes to provide any bulletin-board material regarding the Falcons' decision to let him go.
"I've got nothing bad to say about anybody there," he said. "Sometimes that's just how it goes — you've got to go somewhere else. I'm happy here and just want to go out Sunday and get a win."
Here are five keys to the game:
HOBBLED FALCONS: With the season barely started, the Falcons are already ravaged, and coach Mike Smith said a wave of injuries is the worst in his six years with the team. Three players went on injured reserve after being hurt in last week's win over St. Louis — standout linebacker Sean Weatherspoon, defensive end Kroy Biermann and fullback Bradie Ewing.
The toll is such that Atlanta's defense might be forced to play five rookies against Miami. Undrafted rookies Joplo Bartu and Paul Worrilow are expected to see action at linebacker, the Falcons' thinnest position. And with cornerback Asante Samuel hobbled, rookies Desmond Trufant and Robert Alford — the team's top two draft picks — might both start.
Running back Steven Jackson will miss the game, and Jason Snelling and Jacquizz Rodgers are expected to get the bulk of the carries.
"We're not going to blink," tight end Tony Gonzalez said. "The coaches are going to make adjustments, and we're going to be fine. We're going to go out there and we're going to play our best game, and the players that come in are going to have good games."
VULNERABLE RYANS: Matt Ryan and Miami's Ryan Tannehill have taken plenty of licks already this year.
Ryan was sacked twice and hit eight other times by the Rams, and the Dolphins have a better pass rush than St. Louis. Miami is tied for the NFL lead with nine sacks, led by Wake's 2½.
Tannehill has been sacked nine times, which is tied for the second-most in the NFL, so it's no surprise he was limited in practice this week with a sore right shoulder.
Both teams are likely to throw a lot. Atlanta has run the ball 30 times, fewest in the league, and Miami is averaging only 2.4 yards per carry, third-lowest.
THE TE MIGHT BE OPEN: Gonzalez has been known to scorch the Dolphins, and they've had trouble covering tight ends this year. Indianapolis' Coby Fleener made four catches against them last week, including a 40-yard reception, and Cleveland's Jordan Cameron had nine catches for 108 yards and a score.
Gonzalez has seven catches for Atlanta this season, including one for a touchdown. He has six scores in six career games against Miami.
No one's comparing Charles Clay to Gonzalez yet, but the third-year pro's production has been a pleasant surprise in his first season as a starting tight end. He caught five passes in each of the Dolphins' two games, had a 67-yard reception against Indy and also scored as a fullback on a 1-yard run.
PENALTY-FREE PLAY: The Falcons were the least-penalized team in the NFL last year, but they never achieved what Miami accomplished last week — going an entire game without a penalty.
It was the first time in 15 years the Dolphins played a penalty-free game, a big improvement over the previous week, when they had 10 penalties.
"To have no penalties in a whole game is rare, and that's great," Grimes said. "That's a huge way to give yourself a better chance to win."
Atlanta is again among the league leaders in fewest penalties, with nine for 72 yards.
HOME-FIELD ADVANTAGE?: The Dolphins are the only team with two road victories, and their first home game will test how much their bandwagon is growing.
Miami has endured four consecutive losing seasons while often playing in a half-empty stadium. Home attendance last year averaged 57,375, the lowest since 1980.
But the Dolphins have a chance at their first 3-0 start since 2002, and a near-capacity crowd is expected.
"It's tough playing on the road and winning," Tannehill said. "To come home and play in front of a home crowd with a lot of buzz in the air and hopefully in front of a lot of home fans, it's a lot of fun."