Now they just have to keep playing this way.
"That's who we need to be, consistently," Luck said. "Probably a little bit of soul searching, trying to figure out what we want to be. The truth of the matter is we have the pieces, which is pretty darn obvious."
The Colts (4-5) ended a three-game losing streak, won for the first time in six tries outside the horrible AFC South, and retained their division lead.
Manning, meanwhile, fell 3 yards short of becoming the NFL's career passing leader - after his second interception and two late defensive penalties - allowed Indy to run the final six minutes off the clock.
Denver's quarterback heads into next week's game against Kansas City with 71,836 career yards; Brett Favre had 71,838.
But that was not the record Manning really wanted to break in a venue many credit him with helping build. He'll also have to wait to break Favre's career record for most career regular-season wins (186) by a quarterback after going 21 of 36 with 281 yards, two TDs and two interceptions.
"I've been in enough situations like that in my career where I've been able to focus on the task at hand - trying to win the football game," he said after losing his second straight at Lucas Oil Stadium in what could be his final game in Indy. "I kind of dealt with them (the emotions) a few years ago. I felt like this time coming back was just playing against a good football team."
A team that that was mired in turmoil.
Just five days after firing offensive coordinator Pep Hamilton and giving the play-calling duties to Rob Chudzinski - and four days after Luck wound up on the injury report again - Manning's successor played like the best young quarterback in football. The Colts followed his lead:
-They started fast and finished strong.
-They had no turnovers.
-They committed only four penalties, and the 17-0 lead they took in the first half was their largest of the season. They even ended Denver's first-quarter scoreless streak at seven games when Frank Gore scored on a 7-yard run.
That's exactly what Indianapolis needed, and precisely what coach Chuck Pagano had spent weeks preaching.
"We really feel we've competed with the best football teams in the league - Denver, New England, Carolina," team owner Jim Irsay said. "We still feel we can go the places we dream of going."
They could - if Luck continues playing this way.
Luck could have made it three straight scoring series had he not taken a knee on the final play at Denver's 1-yard line.
"We had to start like we finish, Pagano said. "We finish as good as anybody in football. But we had to put it all together, 60 minutes, and we did."
But they never got the lead.
"We dug ourselves a hole in the first half and showed a lot of character getting out of that hole," coach Gary Kubiak said. "We just weren't able to close the deal after battling our way back. They (Colts) finished it, we didn't."
Daniels caught six passes for 102 yards, and Sanders had six receptions for 90 yards and a TD for Denver.
Copyright 2015 by The Associated Press