If anyone wearing a blue or white practice jersey ever asks why, Jim Caldwell will have a story to tell.

The mantra is to prepare like a starter ever week-a philosophy meant to strengthen players who back up starters-preparing them as best they can in the event that someone is ruled out of the game.

It's "Next Man Up" at it's most rudimentary-but for the Colts head coach, there is a practical example of why the team must always follow it.

"I remember a few years back Montae Reagor was on his way to the ballgame and was in a traffic accident," said Caldwell of the defensive end who was severly injured before the Colts game with the Washington Redskins on October 22, 2006. "This happened hours before the game, so someone had to come up, had to fill in and play.

"If they had not studied, had not been prepared, they certainly wouldn't have fared as well."

While certainly no situation has been as drastic as that one, the Colts have had their share of injuries knock players out for a significant amount of time, and then had an uknown fill in.

Melvin Bullitt was one of those players. An undrafted rookie out of Texas A&M, injuries in three straight seasons to Bob Sanders took him from unknown to solid starter.

Now, in an odd twist of fate, someone must replace him after a shoulder injury has put an end to his season just four games in. Call it the "Next Man Up" for the next man.

"They're doing the right things around here," said DaJuan Morgan-a first year Colts who is one of a few replacements for Bullitt-on his thoughts on why the team replaced injured players so well. "A lot of great coaching preparing guys to step up so when its your turn to step up, the guys are ready to fill in."

Morgan will be expected to this week against the team which he played safety for the past two years-the Kansas City Chiefs. Last season he appeared in 15 games for the club, making 23 tackles but was cut before the 2010 campaign began.

Now he finds himself along with rookie Brandon King as the two expected to step into the role, though Jim Caldwell has yet to name a starter.

"Its just like you approach another week," said Morgan of preparing to play significant time at safety after spending most of the past few games on special teams. "You have to be ready so you don't have to get ready."

While Morgan has some NFL pedigree at the position, King comes in more as Bullitt did a few years ago. The former Purdue Boilermaker was signed as an undrafted free agent back in May and was switched to safety during training camp.

"It seemed like a learning year," said King of his thoughts back in Week One-when both Sanders and Bullitt were healthy. "I thought I would be learning from three great safeties, so I thought it would be a learning year for me, but its turned out to be more than that."

While those two figure to be prominently in the mix for this Sunday's game with Kansas City, Aaron Francisco could be back in the mix in the near future. A member of the Colts in 2009, Francisco was signed again after Bullitt's injury for added depth.

"It was kinda tough to remember somethings but after we went over things in the book yesterday and getting on the field a lot of things started coming back to me a lot quicker," said Francisco of getting reaquainted with the Colts.

Whichever of the three ends up on the field will be paired with veteran Antoine Bethea, who has dealt with a new face next to him for the past five years.

"Run and hit, run and hit," said Bethea simply of what the replacement for Bullitt must do when he gets in there. "Our safeties, thats what we do, we run we hit, and just be in the right positions at the right times and you make plays."