Packers vs. Bears.

It's the NFL's oldest rivalry.

"It didn't mean anything to me before I got here because I didn't understand the magnitude of it," Clay Matthews admitted at his locker Wednesday.  "Now that I'm here it means a great deal to me.  Obviously they are a divisional rival.  We've been playing them since 19-something."

1923 to be exact.  But game number 185 in the series feels a little different for a couple of reasons.

"Short week," says Bears Head Coach Lovie Smith of the quick turnaround from Sunday.  "The preparation time isn't what it normally is for a game week."

The Packers have won six of the last seven games in this storied rivalry, but Green Bay is aware they are preparing for a Bears team that has bolstered its offense.  A year after finishing 24^th in the NFL in total offense, Chicago scored 41 points in week one thanks in part to the additions RB Michael Bush, WR Brandon Marshall, and rookie WR Alshon Jeffery.

Bush, who was brought in to compliment starter Matt Forte, bowled his way in for two rushing scores Sunday,  while Marshall and Jeffery combined for nearly 200 yards and two touchdowns.

"Forte is a special talent," Matthews said.  "Obviously adding Bush is going to help out their run game.  Now getting the receivers, that I think he's been asking for for awhile now in Marshall and the rookie (Jeffery) out there is going to help them out.  They've got some weapons out there, we are going to be ready for all aspects of the game."

"It's a big difference with what we are doing offensively," said Jay Cutler when asked about the difficulty of Green Bay preparing for their new-look offense.  "This is a totally different scheme, mentality and direction we are going offensively so there would be no advantage for them watching tape of last year.  It's totally different."

"You really have one game to go off of," Packers Defensive Coordinator Dom Capers said Wednesday.  "Obviously in the preseason they are going to run their base things.  You've got one game to go off of in terms of coordinator (Mike Tice) calling the game.  You'd like to have more to have a little better feel for the tendencies, but we know their personnel well."

That includes Brandon Marshall, who torched Green Bay for 10 catches and 127 yards in 2010 in helping Miami upset Green Bay at Lambeau Field.  He's just one new face to look out for when the NFL's oldest rivalry renews Thursday.

"I'm glad I am in it," said Marshall.  "Playing against the Packers, at Lambeau, as a Bear, that's big."