Due in large part to an aggressive defense leading the league in takeaways, the Tennessee Titans are one of three NFL teams still undefeated.
The Baltimore Ravens know a little something about being atop the defensive charts themselves.
A pair of the NFL's stingiest defenses will clash on Sunday in Baltimore when the Titans look to improve upon the fastest start in franchise history against the Ravens.
Tennessee (4-0) has endured a quarterback change and a shaky wide receiver situation to not just win its first four games, but win them convincingly. The Titans - who have won a league-high seven straight dating to last season - haven't yet trailed in the second half, and are winning by an average margin of two touchdowns in 2008.
A lot of the credit goes to Tennessee's defense, which is allowing an NFL-low 11.5 points per game and has forced a league-high 12 turnovers - four of them coming in last week's 30-17 victory over Minnesota.
"This team is built on letting the defense go out there and win the game," said defensive tackle Albert Haynesworth, who leads AFC linemen with five sacks. "We've got the components to be a great defense. We still haven't played a complete game, but we're getting better and better, so hopefully you'll see it soon."
A suffocating defense is the tradition in Baltimore (2-1), which has ranked among the NFL's top six in total yards allowed in each of the last five seasons. The Ravens, who boasted the league's top-ranked unit in 2006, are ranked first again, allowing 186.7 yards per game - nearly 50 fewer than the second-place Steelers.
Baltimore looked like it was headed for a 3-0 start on Monday in Pittsburgh, where it jumped out to a 13-3 halftime lead. The Ravens, though, gave up two touchdowns in a 15-second span of the third quarter - one on a Joe Flacco fumble deep in his own territory - and went on to lose 23-20 in overtime.
"There's nothing you can say about this game other than the fact that a couple plays went against us that we need to play better in," first-year coach John Harbaugh said. "Aside from that, our guys played well enough to win."
Baltimore, which also features the league's second-ranked rush defense (69.7 ypg), will be challenged by a pair of solid runners. Titans rookie Chris Johnson is averaging 5.0 yards per carry, and LenDale White has scored five touchdowns.
Johnson scored twice and White once in last week's win.
Johnson had 109 yards rushing in his only previous road game, a 24-7 win at Cincinnati in Week 2, but the odds are against him repeating that effort this week - the Ravens have gone an NFL-high 22 games without allowing a 100-yard rusher.
Tennessee coach Jeff Fisher has stuck with veteran quarterback Kerry Collins after an injury and motivation questions surrounding Vince Young, and Collins has done just what he's been asked - move the ball while limiting mistakes. Collins has only one interception and has been sacked once in three starts.
"Bottom line, I'm on a good football team,'' said Collins, who hasn't started against the Ravens since 1996, when he was with Carolina. "Are we a great football team yet? No, I don't think so, but finding ways to win and winning ballgames just keeps adding to the confidence, keeps adding to the makeup of your team.''
Collins and the Titans have one important statistic working in their favor. Since 2000, 25 teams have started a season 4-0, and only three have failed to make the playoffs - none since 2003. Linebacker Keith Bulluck isn't about to celebrate, though.
"We still have a chance to go 4-12,'' he said.
While Collins has started 152 career games, Sunday will be Flacco's fourth start. Baltimore's rookie quarterback didn't throw an interception Monday night despite heavy pressure from Pittsburgh's defense, but he fumbled twice - losing the one that cost the Ravens the lead.
"He didn't get rattled,'' said Baltimore receiver Derrick Mason, who spent his first eight seasons in Tennessee. "He showed poise out there and that's all you can ask your young quarterback to do. But we've got to help him out.''
Mason, who had 137 yards receiving and a touchdown Monday, may need to make more plays on Sunday to help out a banged-up running game. Willis McGahee injured his ribs against the Steelers and his status is unclear, though fullback Le'Ron McClain (4.1 ypc, three touchdowns) has filled in nicely.
The Ravens and Titans have split their last two meetings, both in Tennessee. Their last game in Baltimore was a 20-17 Titans victory in a wild card playoff meeting Jan. 3, 2004.