Colts sources told ESPN senior NFL analyst Chris Mortensen that although Manning is making some progress since having neck surgery and has maintained optimism, the team's hierarchy does not believe he will be ready when Indianapolis opens the season Sept. 11 at Houston.
Polian had been talking to Collins, who had announced his retirement earlier this year, for several days before Collins agreed Tuesday night after getting the green light from his wife.
In order to lure Collins back to the NFL, the Colts will pay him $4 million this season, league sources told Mortensen. The sources also said it is a two-year contract with an unknown total value, but structured, in essence, to be a one-year deal.
Collins said he has been given no indication that Manning won't play at Houston.
"Hopefully, Peyton will be back, but if he's not maybe I can be one of the guys that can help this ball club," Collins said in a conference call with reporters Wednesday night. "The biggest draw for me coming here was just being with a team that I have a lot of respect for and a lot of history with, and really to be with a great team and play with one of greatest quarterbacks of all time."
As general manager of the expansion Carolina Panthers, Polian drafted Collins with the fifth overall pick in the 1995 draft. Polian was unsuccessful in trying to sign Collins in 2006 when the quarterback chose to sign with the Tennessee Titans instead.
Not every player liked the move.
"We don't even know him, we ain't vanilla, man, we ain't no simple offense," receiver Reggie Wayne said. "So for him to can come in here and be the starter, I don't see it. I think that's a step back."
Wayne, a five-time Pro Bowler and one of Manning's favorite targets, has supported backup Curtis Painter. And while he called Collins "a great guy," he said he was worried about the Colts getting better.
"Who says Kerry's going to be the starter?" Wayne said. "Just because we bring him in doesn't mean he's the starter. He's got to learn too, right? Unless they gave him a playbook months ago, he's got to learn to.
"I don't care who you are, I mean I'm not going to let anyone just come in here and just push someone (like Painter) aside like you're that dog now, you know what I mean?" Wayne added.
Owner Jim Irsay first announced Collins' addition on Twitter, and the team confirmed the move in a news release Wednesday.
"It is a good opportunity to have Kerry become part of the team," Colts coach Jim Caldwell said in the team's release. "He is a veteran quarterback who has started many games and he brings dimension and depth to the quarterback position, which will be helpful. He is familiar with our division and will make a great addition to our roster."
Caldwell was a member of Penn State's coaching staff when Collins was leading the Nittany Lions.
The 38-year-old Collins retired during the lockout in July, saying "while my desire to compete on Sundays is still and always will be there, my willingness to commit to the preparation necessary to play another season has waned to a level that I feel is no longer adequate to meet the demands of the position."
He was a free agent after spending the past five seasons with the Titans.
Besides Carolina, he also has played for the New Orleans Saints, New York Giants, Oakland Raiders and Titans in 16 seasons. He has thrown for 40,441 yards with 206 touchdowns and 195 interceptions and was a two-time Pro Bowl player (1996, 2008).
Manning said Saturday he will use the next two weeks to get healthy from the offseason neck surgery, a timeline that could jeopardize his streak of 227 consecutive starts. Manning signed a five-year, $90 million contract in July after the 4½-month lockout ended.
"I certainly want to be out there, and it's hard to keep track of the hours I've spent in rehab," he said. "I was shortchanged a little bit by the lockout and I'm going to need every bit of the next two weeks, and then I can give you more of an update with where I am."
Since being the No. 1 overall pick in the 1998 draft, Manning has started all 208 regular-season games and 19 more in the playoffs, the second-longest streak for a quarterback in league history behind only Brett Favre.
But the recovery from the second operation on his neck in 15 months has been slower than expected.
"I have made progress, but I still have some work to do," he said. "When I'm healthy enough, I'll be able to play."
Painter has started both preseason games and has completed 8 of 16 passes for 95 yards with no touchdowns and one interception. In Friday night's 16-3 loss to Washington, Painter had one first down and couldn't get the offense past its 29-yard line despite playing the entire first half.
Painter hasn't played in a regular-season game since relieving Manning in the final two games of the 2009 season -- after the Colts had already locked up home-field advantage throughout the playoffs. His career numbers are 8 of 28 for 83 yards with no touchdowns, two interceptions and a quarterback rating of 9.8.
For his part, Painter doesn't expect it to take Collins long to get up to speed.
"He's a veteran guy, been around a while, I'm sure the terminology across the league isn't too different," Painter said. "I expect he'll come in and pick it up quite well."
The only other time Manning's streak was in jeopardy was 2008, when he missed all of training camp and all the preseason after undergoing surgery twice to remove an infected bursa sac from his left knee. He struggled early that season before going on to win the third of his four MVP awards.
Information from ESPN senior NFL analyst Chris Mortensen, ESPN.com senior NFL writer John Clayton and The Associated Press was used in this report.