He never imagined he would receive the call in Week 1.
"I know what it takes to prepare and be successful in this league, so I'm going to do all those things, rely on all the experience that I have," Collins said. "I have a good idea of what I need to do to get ready to play and give a winning performance."
Collins has the kind of résumé most teams want in a backup quarterback.
But now Collins finds himself in the toughest predicament of his career.
He has had less than two weeks to learn the Colts' pass-first offense, which traditionally has called plays at the line of scrimmage. He didn't play a preseason snap with Pro Bowl picks Reggie Wayne or Dallas Clark, and the Colts haven't rushed for more than 4.0 yards per carry since their 2006 Super Bowl season. Plus, the Colts will open the season with three new starters on the offensive line and a fourth, former right tackle Ryan Diem, moving inside to guard.
Collins must overcome all of that with a whole city ready to pounce on his mistakes if he fails.
"It's not as if we're dealing with someone who hasn't been in a lot of games. He's played, he understands concepts and systems, and he'll be able to function, I think, very, very well," coach Jim Caldwell said. "I don't expect him to be perfect. We have to have some other guys step up and give him some assistance here and there.
"We have a lot of guys who can do that, and I think he'll be fine."
The toughest part will be trying to match Manning's high standards.
During his streak of 227 consecutive starts, Manning has led the Colts to 11 playoff appearances, 11 double-digit win seasons, eight division crowns, two AFC titles and the first NFL championship in the franchise's Indianapolis era.
The streak, second-longest among NFL quarterbacks behind only Brett Favre, has gone so long that no player in the Colts' locker room has started a game in blue-and-white without No. 18 calling the signals.
So when word came Monday that Manning's slow recovery from offseason neck surgery could end the streak, fans wasted no time in voicing their concerns.
Most fans believe Indianapolis will not become the first team to play a Super Bowl in its home stadium. Many see the Colts even falling short of making the playoffs for a record-breaking 10th consecutive year, and some suggest the Colts will be lucky to finish with more than six wins if Manning is out for an extended period.
Don't tell that to Collins, 38, or his new teammates.
"I can't imagine trying to learn something as complicated as (our offense), as quickly as he has," Pro Bowl center Jeff Saturday said. "He did a great job and put the ball where it needed to be (against the Cincinnati Bengals). There are little things that we need to clean up, but other than that, I've got full confidence that if he's the guy, we'll be ready."
Football should be the easy part for Collins, who overcame a very public battle with alcohol and personal issues in Carolina, made a remarkable comeback in the spotlight of New York, then survived the unending quarterback controversy with Vince Young in Tennessee.
But replacing Manning, well, that is a little different.
"For so many years, I've watched him do it, and I've always kind of wondered, `What's he doing?' I think everybody does," Collins said last week. "Now, to be in it and to see what he does and how he does it, is a real thrill. From a quarterback standpoint, I think we all kind of look at this and are kind of envious in a way to just how well he does it, and what this offense is about."
After signing oAug. 24, Collins called himself the "just-in-case" guy.
"I feel comfortable with the offense," he said. "I feel like I've come a long way in the short time since I've been here. I've really buckled down and grinded on it. Certainly I've got a lot to learn, but as far as my comfort level, it's pretty high."
Copyright 2011 by The Associated Press