Head coach Mike McCarthy said Monday that Collins suffered a strained ligament in his left knee during the third quarter of the 33-22 win at Kansas City on Sunday.
The nature of the strain wasn't disclosed, but McCarthy said Collins would be out at least a couple weeks. Surgery won't be needed.
"It looked a lot worse on film," McCarthy said. "The evaluation (Monday) was actually positive. The MRI was positive, based on what (team doctor) Pat McKenzie said, because we all figured the worst the way he went down."
In steps Rouse, a third-round draft pick. He played most of the second half Sunday and received a positive assessment from the coaches, but it was only his second game in which he had playing time on defense.
Rouse missed an extended period early in the season because of a hamstring injury. McCarthy, though, feels the former Virginia Tech standout is up to speed in the scheme and can be effective in a full-time role.
"He's done a nice job. He's very bright," McCarthy said. "If you go back to the OTAs, he picked up the defense very quickly. It's his opportunity, and a lot of young players get their opportunity this way. I have no concerns about him. You don't really know until they play in the real games, and it's his time."
Rouse is an intriguing prospect as a safety because of his 6-4 size and athleticism.
Believe it or not, they're 7-1
Even after making two incredible deep touchdown passes to win a pair of road games in a span of seven days, veteran quarterback Brett Favre still can't help but wonder if these youth-dominated Packers really are 7-1.
"It's hard to doubt us," Favre said after a 33-22 comeback victory at Kansas City.
His 60-yard scoring strike to Greg Jennings -- the two also hooked up for an 82-yard touchdown on the first play of overtime at Denver on Monday night -- put the Packers ahead to stay at 23-22 with three minutes left in a seesaw game.
Despite having a short turnaround from the previous game and going right back on the road, the Packers improved their away record to 4-0 and have won six straight outside Lambeau Field, dating to the end of last season.
The Packers are one game ahead of Detroit for first place in the NFC North at the midway point of the season. Many picked Green Bay to finish no better than the 8-8 record it attained in 2006 by winning its final four games.
"You can question us. I do, too," Favre said. "Did I think we were blowing chances (Sunday)? Absolutely. Did I think we were running out of time? Absolutely. Did I think we could do it? Sure. Week in and week out, I keep saying that it's very difficult the way we're doing it. I would like to make it much easier. But, somehow, we're doing it."
Flags are flying against Packers
Aside from its sputtering run game, the biggest blemish on Green Bay's torrid start is the frequency of penalties it's committed in recent weeks.
The Packers were charged with 13 infractions, totaling 115 yards, on Sunday. They also had 13 against the Broncos, amounting to 103 yards of walk-offs. Green Bay also was penalized 12 times for 93 yards in the Week 5 loss to Chicago.
"The pre-snap penalties, there's no excuse for," head coach Mike McCarthy said Monday. "I'm not going to sit here and say that's OK. You don't jump offsides. ... You don't false start. There's no excuse for that."
Two of Green Bay's penalties the last two games were the result of a player kicking the football. Running back Vernand Morency was the guilty party Sunday, when he kicked the ball out of bounds in an effort to keep possession with the Packers on a play that was initially called a lateral pass -- the call was reversed on replay review to an incomplete pass.
McCarthy lauded Morency for being instinctive by making the kick but acknowledged that it's a lesson learned not only for him but the entire team about what's out of bounds in the rulebook.
"When you make mistakes that are in a competitive nature, an instinctive nature, trying to eliminate a bigger mistake, those are the kind of things you can live with," McCarthy said. "It's the pre-snap penalties, the poor-judgment penalties are the ones you need to eliminate from your game."