The Indianapolis Colts were the NFL's last unbeaten team in three of the last five seasons, so they know a thing or two about running in front of the pack.

For the surprising Kansas City Chiefs, it's a little bit surreal.

The Chiefs are the league's lone team without a loss, a perfect record that may be difficult to preserve Sunday as they seek their first win in Indianapolis over the Colts, who are eager to move on after a heartbreaking defeat.

Indianapolis (2-2) has been the NFL's regular season standard for much of the past decade, entering this season with a league-best 89-23 record since the start of the 2003 season.

The Colts have been undefeated through at least seven games in four of the past five seasons -- and in 2005, '08 and '09 were the league's last unbeaten team -- but perhaps no one expected the Chiefs (3-0) to be in that role early in 2010.

Kansas City has done it by relying on an impressive rushing attack (160.7 yards per game, third in the NFL) and opportunistic special teams unit featuring rookie returners Dexter McCluster and Javier Arenas, emerging as the only AFC West team with a winning record.

Not bad, considering the Chiefs didn't win their third game until late November last year and never got there at all in 2008.

"It feels good. This is what we've been talking about in OTAs, minicamp, training camp," cornerback Brandon Flowers said after a 31-10 win over San Francisco in Week 3. "We just have to keep it going, we can't settle for 3-0."

Even after a convincing victory, Flowers was pleased Kansas City had an early bye week.

"That means we can get extra film study, extra time to get ready for going against the Colts and Peyton Manning, and that high-powered offense. That can take us a long way."

The Chiefs are looking to become the eighth team to open 4-0 after beginning the previous season 0-4, but they'll have their work cut out for them. Kansas City has lost in each of its four trips to Indianapolis and is 1-9 against the Colts -- three playoff defeats included -- in the last 10 meetings.

To make matters worse, the Chiefs may be facing Manning's club at the worst possible time -- coming off a loss. Only three times since 2005 has Indianapolis dropped consecutive games when Manning has played 60 minutes.

Sunday's loss in Jacksonville was particularly vexing for the AFC champs. Manning threw for 352 yards and two touchdowns, but two red-zone turnovers and a dropped interception came back to haunt the Colts when Josh Scobee's 59-yard field goal at the gun gave the Jaguars a 31-28 win.

Indianapolis is 0-2 in the AFC South for the first time.

"It's not what we want to be, it's not what we set out to be, but it's what we are," said Manning, who leads the league with 11 touchdowns and a 112.2 passer rating. "We have to find a way to dig ourselves out of a hole. We are in a hole."

The Colts' mediocre start is due in large part to issues with the run -- on both sides of the ball. Indianapolis is 29th (75.5 ypg) on the ground offensively, rushing for fewer than 60 yards in three of four games, and 29th against the run, yielding 149.5 per contest.

That doesn't bode well considering what Kansas City does best. Fourteen running backs are averaging at least 70 yards on the ground, and in Jamaal Charles (79.3) and Thomas Jones (72.3), the Chiefs have two.

"There's obviously, a lot of work to do on that side of the ball and we've got to get that straightened away," Colts president Bill Polian said of his team's defense. "We've got good players there, but they're not playing well right now."

Indianapolis is missing a few key ones in the secondary. Safety Bob Sanders is expected to miss most of the regular season with a torn biceps, and replacement Melvin Bullitt is out for the year after breaking a bone in his shoulder against Jacksonville.

Rookie Brandon King or recently signed DaJuan Morgan will likely replace Bullitt on Sunday, leaving Matt Cassel -- who threw for 250 yards and three TDs against the 49ers -- with a potential weakness to exploit.

A Chiefs loss will leave the NFL without a 4-0 team for the first time since 1970.