With Atari Bigby out with a knee injury, Nick Collins' status uncertain due to an injury and Aaron Rouse no longer on the roster, who will be in the starting lineup at safety on Sunday for the Packers at St. Louis is up in the air.

Rouse, a third-year player who started at strong safety in place of Bigby this past Sunday against Cincinnati, was released on Wednesday morning by the Packers. His roster spot was filled by free-agent safety Matt Giordano, who spent his first four seasons in the NFL (2005-08) with Indianapolis before being released just prior to the start of the regular season.

"In our conversation with (Aaron) I just felt that his ability to be consistent and the growth part of it is one of the reasons that we made the change," McCarthy said. "But there are other factors involved based on availability, without getting into all of that. That's really the landscape of personnel in the National Football League, timing and things like that, special teams. That was all part of our decision."

This was the second time the Packers made a move at safety this month. Offseason free-agent acquisition Anthony Smith was released in the final roster cutdown as the team acquired safety Derrick Martin in a trade with the Baltimore Ravens. With Bigby expected to be out for at least another three weeks and Collins' availability up in the air for Sunday, the team elected to make another change on Wednesday.

Collins sustained a chest injury in the second quarter of Sunday's game vs. the Bengals when another player landed on him during a tackle and did not return, with Jarrett Bush replacing him for the remainder of the contest. McCarthy said Collins was off to one of the better performances of his career, evidenced by his seven tackles and a pass defensed in just a quarter and a half of playing time.

Collins has proved to be a durable player in his first four seasons, with the only missed games in his career coming in 2007 when he was sidelined for three contests with a knee injury. He played in all 16 games last season on his way to a Pro Bowl berth despite battling back and shin injuries.

Collins was limited in practice on Wednesday, and called himself "day-to-day". McCarthy said he anticipates that Collins will be able to play on Sunday, but that his week of practice will ultimately determine his availability.

"I'm a guy who always wants to be on the field," Collins said. "I'm a leader, so I just want to go out there and lead by example and show them you can fight through any type of pain if it is not too bad. That's my main focus, to try and help this team win.

"If I am able to play, I'll play, but if not I'm going to still be with them. I'm going to coach up the guys that are in the game and hopefully we can get the job done."

If Collins can't play, Martin and Bush are expected to get their first starts with the Packers at safety with Giordano as the backup. If Collins can go, either Martin or Bush would start next to him with the other as the top backup, and McCarthy said Wednesday that the week of practice will help the coaches make that decision.

"It's a real challenge for our assistant coaches, no doubt," McCarthy said. "Dom Capers, Darren Perry and I talked about this extensively over the last couple of days, so obviously a lot of thought goes into these types of decisions. We're confident that we'll have our players ready to go for Sunday in St. Louis."

Martin played in the first two games, contributing on special teams with three tackles, which ties him for second on the team. He played cornerback for his first three seasons with Baltimore before making the switch to safety this offseason with the Ravens in their 3-4 defense, and said the similarities between the two schemes have made the transition easier for someone trying to get up to speed in a relatively short period of time.

"It helps a lot," Martin said. "Like I said when I got here, it was just terminology that I had to switch around. Flip a couple of things out, and once I did that, it's pretty much downhill from there. I can just play football.

"You know somebody is going to get hurt and you know something is going to happen, the ups and downs during a season. You have to be able to play when it is your time to play. You've got to be able to step up when it is your turn to step up."

The word that Rouse was released on Wednesday morning wasn't the only significant news for Martin this week, as his wife gave birth to their second child, a baby girl, on Monday. Although he said he prepared for both of the first two games as if he could play on defense, Martin admitted the situation this week is a little different.

"There is more of a sense of urgency," Martin said. "When you're not sure who is going to be playing, you're like, 'I can learn this and then I can wait to make sure I know it.' But when you think you might be in, you have to learn it right now. After the three weeks leading up, I feel like I've got a good grasp on the defense."

{sportsad300}Giordano will be trying to play catch-up just like Martin was a few weeks ago. McCarthy said the team liked the versatility that Giordano brings since he started games at both safety spots during his time with the Colts, as well as his special-teams abilities.

Giordano has familiarity with quarterback Aaron Rodgers, having been a teammate of his for two seasons at California. They also squared off against each other when Giordano's Fresno City College team handed Rodgers' Butte College team its lone defeat in 2002.

"Yeah, he reminds me," Rodgers said. "It is funny though because we put up 600 yards of offense against them and still lost the game, so I remind him of that every time he reminds me that they were the only team to beat us."

Giordano got off to a good start with two interceptions in his first practice on Wednesday, including one off his former college teammate. Facing uncertainty himself as far as his role for Sunday, Giordano's focus is on getting up to speed with the playbook as quickly as he can in case he is pressed into duty.

"It's definitely an opportunity, but the thing I've got to do now is just retain as much information and know this defense as quickly as possible and execute my assignment right now," Giordano said. "I think it's kind of like learning a new language. I have learned and played with a language for four years in Indianapolis, and this one I've got to learn in about four days. I'll be cooking the books, but I'll be ready come Sunday."