Part of the reason Hillenmeyer decided to sign with the Bears is the Packers used their first round pick on Nick Barnett, who played the bulk of the snaps at middle linebacker in the preseason.
"To be the seventh linebacker on a team is a bad situation," Hillenmeyer said. "When you're on the 53-man roster but you don't play, you don't get a chance to make plays and it's hard to get buried down the depth chart in that situation."
It took some time for Hillenmeyer to feel at home with the Bears. After a brief stint on the practice squad he was elevated to the 53-man roster for the fourth game of the season. His role was limited to special teams and a handful of snaps at linebacker.
Just as he felt comfortable with the system, the coaching staff was fired at the end of 2003. With head coach Lovie Smith in place, the Bears looked to turn things around after going 11-21 the past two seasons.
A bad break for the team turned out to be Hillenmeyer's opportunity to make an impression. Brian Urlacher suffered a hamstring pull during the first practice in training camp and Hillenmeyer suddenly had a chance with the first team defense.
"When we had the new coaching staff in here it gave me a clean slate," Hillenmeyer said. "It's hard to come in for any rookie where everybody already knows what they're doing and they sort of catch the rookie up. When you have a new coaching staff come in everybody starts from square one so that gave the chance to know the defense as well as anybody. I think gave me a leg up just because I need to use that mental part of the game to get my advantage."
Hillenmeyer went on to start 11 games in 2004, with seven starts at middle linebacker and four on the strong side. He had 90 tackles, 2.5 sacks and a forced fumble.
Still the Bears weren't sure if the six-foot-4, 238-pounder was ready to complete their trio of linebackers with Urlacher and Lance Briggs. Several veterans were considered during free agency, but ultimately the Bears felt Hillenmeyer was the best option.
The third-year linebacker has moved past a reputation for just being a smart, fundamentally sound player to one that can make game changing plays on the top defense in the NFL. He has 58 tackles, an interception and one sack.
"It's fun," Hillenmeyer said. "It's definitely the best defense I've ever been a part of. I think we've got a really good thing going here.
"We've got everybody out there making plays, especially in the last couple weeks our d-line has been unbelievable. Whenever you've got that going people are competing with each other to make plays out there. There are only so many plays to be made in a game and it's a race to see who can make them and that's a fun way to play football and a fun way to help your team win too."
That's exactly what Hillenmeyer hopes to do Sunday against the team that brought him into the league.
"I don't hate the Packers," Hillenmeyer said. "I don't wish they would lose every game. But as far as the rivalry goes I'm all Bear. There's no part of me that's conflicted at all.
"I was drafted by Green Bay so that's where I started, but as far as where I feel like my home is it's definitely here."