But they sure looked a whole lot more like themselves Thursday night.
All it took was a trip to Atlanta.
Manning threw three touchdown passes, Anthony Gonzalez had 105 yards receiving and the defending champs, after getting stunned with 10 quick points by the Falcons, rebounded for a 31-13 victory.
"They jumped out early," Manning said. "We finally got on track, got the lead and put them away."
Indianapolis (9-2) had struggled the past three weeks, losing twice and pulling out a lackluster home win over Kansas City. The Colts' malaise carried over the first quarter at the Georgia Dome, with the Falcons striking for Morten Andersen's 34-yard field goal and Joey Harrington's 48-yard touchdown pass to Roddy White.
But any thoughts the Falcons (3-8) had of pulling off a huge upset were quickly wiped out by Manning. He threw all three of his TD passes in the second quarter, going 23 yards to Reggie Wayne, 8 yards to Dallas Clark and 5 yards to Ben Utecht.
"It was frustrating because we came out so strong," Falcons quarterback Joey Harrington said. "We were firing. But you know the defending Super Bowl champs are not going to roll over and die."
Gonzalez didn't get to the end zone, but he was Manning's favorite receiver. He hauled in a 35-yard pass that set up Wayne's TD and a 32-yarder that led to Clark's score.
Manning was 22-for-32 for 272 yards and went past another Colts great, Johnny Unitas, for 10th place on the NFL's career passing list with 40,407 yards. He also broke a tie with Warren Moon for fifth place in career TD passes, moving to 294.
"I'm a big fan of quarterbacks," Manning said. "I have great respect for Warren Moon. I never got to see Unitas, but my dad (former pro QB Archie Manning) told me what an impact he had on him."
After missing the past two games with a broken thumb, Gonzalez's return was a boost for a Colts' offense still plagued by injuries. Perennial Pro Bowl receiver Marvin Harrison missed his fifth straight game with an ailing left knee. Indy also had to go without two starting linemen, Tony Ugoh and Ryan Diem.
Not to worry, not against the Falcons. The Colts rallied for a 21-13 lead by halftime, and Atlanta just faded away over the final two quarters, managing just 92 yards after the break. The Falcons wrapped up a stretch of two home games in five days in which they lost twice by a cumulative score of 62-20.
This was supposed to be a Manning vs. Michael Vick prime-time matchup. But Vick was sitting in a jail cell, having turned himself in Monday to begin serving his expected prison sentence for dogfighting.
It was Vick's off-the-field pursuits that put Atlanta in such a mess, assured of another non-winning season with five weeks still to go.
The only highlight for the Falcons was Warrick Dunn becoming the 22nd rusher in NFL history to reach 10,000 yards. He made it on a 2-yard run early in the second quarter, earning a standing ovation from the Georgia Dome crowd.
"I've just been consistent over the years," said Dunn, who finished the night with 10,044 yards. "Over the last few years, I've been able to get into a groove and play at a high level. I just kept fighting hard, training hard, practicing hard, and let my skills take over."
Dunn's milestone was about the last time anyone heard from the home fans, though there were plenty of blue-wearing Indy boosters -- most of them in Manning's No. 18 jersey -- to liven things up.
The Colts are still on course to lock down a first-round bye and home field for at least one playoff game, though they're not quite on top of their game.
Manning was sacked a season-high four times and also threw an ugly pass near the Atlanta goal line that was easily intercepted by DeAngelo Hall. Linebacker Michael Boley had three of the sacks for the Falcons.
But the Colts took advantage of a big break when Atlanta's Demorrio Williams was called for running into punter Hunter Smith in the second quarter. Williams barely touched Smith, but the punter went down like he'd been punched and the flag came flying.
"That's so bad!" Falcons special teams coach Jerry Rosburg screamed.
Manning drove the Colts quickly for the go-ahead touchdown, and they never looked back. The Indy defense held Atlanta to a field goal over the final three quarters.
Harrington, starting again with Byron Leftwich sidelined by a tailbone injury, completed just 14 of 30 for 155 yards with two interceptions. White had his third 100-yard receiving day of the season, with six receptions for 104 yards.
Boley (elbow) and Colts RB Joseph Addai (neck) both left with injuries that looked potentially serious, but returned to the game. Addai scored Indy's other TD on a 4-yard run. ... The Colts improved to 13-1 in their history against the Falcons, the best record for any head-to-head matchup of at least 10 games. ... Next up for Manning on the yardage list: Joe Montana at No. 9 with 40,551.