Led by the highest-scoring offense in the NFL, the Indianapolis Colts are one of three remaining undefeated teams. While the offense is surging, the defense is a causing concerns for coach Tony Dungy.

The Colts look to remain unbeaten and improve on some of their defensive miscues Sunday when they host the winless Tennessee Titans at the RCA Dome.

Indianapolis (4-0) has scored 121 points this season - one of just three teams in the league to surpass the 100-point mark - and has led the AFC in scoring the last two seasons.

The Colts scored 17 fourth-quarter points in their 31-28 win over the New York Jets last Sunday, but the defense missed tackles, got into the wrong coverages and failed to hold off the Jets.

"We have to play better and the guys we're playing have to play better," Dungy said. "For the most part, our problems were tackling and not knowing the coverage, and we have to get better at that."

Indianapolis allowed 321 total yards to New York, which converted 7-of-13 third down attempts.

On the season, the Colts have allowed the second-most rushing yards in the league at 620, as opponents are gaining an average of 4.8 yards per rush.

"We're just not sharp," Dungy said of Indianapolis, which was also penalized 10 times. "We have to be better, and we will be."

A game against the struggling Titans (0-4) should help the Colts clean up their mistakes.

Indianapolis has won six straight games over Tennessee, and outscored them 66-13 in sweeping the series last year.

Peyton Manning is 6-2 in eight career games against the Titans, passing for 2,155 yards with 16 touchdowns and six interceptions.

Manning went 21-of-30 for 217 yards with both a passing and rushing touchdown last Sunday. He was 6-of-8 for 60 yards on the Colts' final drive, scoring on a 1-yard run with 50 seconds left for the game-winning score.

"I was pumped," said Manning, who has scored a rushing touchdown in consecutive games for the first time since 2001. "You practice those two-minute drills all the time."

Manning has thrown for the second-most yards in the NFL this season with 1,112, and has six touchdowns to just one interception.

Marvin Harrison moved past Andre Reed and into fourth place on the NFL's career receptions list last Sunday with his 952nd catch. He has 29 receptions for an NFL-best 413 receiving yards, and has 60 receptions for 732 yards and six touchdowns lifetime against the Titans.

The Colts, along with the Baltimore Ravens and Chicago Bears, are the only undefeated teams in the league, and a win Sunday would give them their third 5-0 start in the last four years.

Indianapolis is 16-2 at the RCA Dome since the start of the 2004 season, while Tennessee is just 4-14 on the road in that span.

The Colts have outscored the Titans 119-34 in their last three home games.

Vince Young makes his second NFL start Sunday, after a rough first one in Tennessee's 45-14 loss to Dallas last Sunday.

Young, the No. 3 overall pick in April was 14-of-29 for 155 yards with a touchdown, two interceptions and a fumble. He did show flashes of potential, though, when he scored a 2-point conversion on a draw.

"I learned that you've got to take care of the ball for one, and then also don't try to put too much on yourself," said Young, who is 24-for-53 for 288 yards, with two touchdowns and three interceptions this season.

The already struggling Tennessee defense must fill the hole left by defensive tackle Albert Haynesworth, who is suspended for the next five games for kicking Dallas center Andre Gurode in the face during Sunday's game.

The Titans allowed the Cowboys to gain 217 rushing yards, and have allowed an NFL-worst 708 rushing yards. They also have the third-worst scoring defense in the league, allowing an average of 30.2 points.

Tennessee is in the midst of its worst start since 1984, when it started 0-10 while the franchise was located in Houston. The Titans have seven straight losses since last December - the longest skid under coach Jeff Fisher and the worst since 11 straight losses in 1994.

"It's embarrassing to go out and have the scoring discrepancy at home like we did. That was not fun," Fisher said of the most recent loss. "It's by no means the start we expected. It is what it is, and all we can do is move forward."