INDIANAPOLIS — Tony Dungy won't change his philosophy.

He intends to play his regulars this week, build momentum for the playoffs and try to put the Indianapolis Colts in the best possible playoff position — even though they no longer control their seeding fate.

"We've got to treat this like a must-win game," he said yesterday. "We need to win to stay ahead of New England and put pressure on Baltimore."

A month ago, the Colts (11-4) appeared headed toward earning a second straight No. 1 seed in the AFC playoffs. Their late-season collapse has ruined everything.

Back-to-back losses at Tennessee and Jacksonville left San Diego in the lead for home-field advantage, and Sunday's demoralizing loss at Houston may have cost Indy a shot at the coveted first-round bye, too.

More troublesome are the problems that seem to get worse with each passing week.

The league's worst run defense took another hit Sunday when Ron Dayne rushed for a career-high 153 yards and two touchdowns — only the third 100-yard game of the former Heisman Trophy winner's seven-year career.

By successfully playing keepaway, opponents also have managed to beat two-time MVP Manning the one way he can't control: making him a spectator. Manning has spent more time in recent weeks studying photos on the sideline than picking apart defenses on the field.

And four losses in six games, including four straight on the road — another ignominious first during Dungy's Indy era — have left the Colts in the unenviable position of trying to turn things around in the playoffs.

It's an unusual predicament for the first team in NFL history with consecutive 9-0 records, which is not accustomed to watching the scoreboard in late December.

"I don't think it's confidence, I think there's disappointment and frustration that we're not getting it done," Dungy said. "We have to fix it if we want to get where we want to go."

Clearly, though, time is running short.

The Colts close the regular season Sunday at home against Miami before likely opening the postseason against an AFC wild-card team. The worries are mounting.

Only a victory over the Dolphins and a win by Buffalo at Baltimore would give Indy the No. 2 seed.

But the uncharacteristic scenarios are also creating some unusual moments for these Colts.

Dungy called the Houston loss his most disappointing in five seasons with Indianapolis because he thought his team played like nothing was at stake.

Manning was even caught by television cameras pleading with the defense to give him another chance late in the third quarter, something Dungy said the defense was already telling itself.

"I think we're all frustrated to a certain point, and we didn't get it for him enough yesterday," Dungy said. "But nobody's more frustrated than the defense."