Two weeks ago, Brian Urlacher scoffed at the notion that the Bears defense is showing its age.
"Yeah, we're getting old," he deadpanned. "I hear that every year."
He's hearing it again this week. The creaky-kneed linebacker will miss Sunday's game against the Vikings -- and possibly the rest of the season -- because of a hamstring pull.
And the, well, aging Bears will miss him. Tied with the Packers for the NFC North lead at 8-4, they are trying to recover from a stretch of three losses in four games.
Their 7-1 start was fueled by a defense that followed coach Lovie Smith's "tackle hard and take the ball away" philosophy to perfection. In their first eight games, the Bears returned seven interceptions for touchdowns and forced 28 turnovers, five when opponents were inside the Bears' 20.
That unlikely pace hasn't continued. Chicago lost to San Francisco and Houston before its 28-10 victory over the Vikings two weeks ago. But particularly telling was an overtime loss, at home, to Seattle last Sunday.
The Bears allowed a 12-play, 97-yard touchdown drive by the Seahawks at the end of regulation, then a 12-play, 80-yard touchdown drive on the opening possession of overtime. And both Urlacher and cornerback Tim Jennings, who leads the NFL with eight interceptions, were injured. Neither will play Sunday.
"It wasn't a good football performance," Smith said. "For us, it's kind of simple: You have to get off the field on third downs. And those two long series, we were on the field a long time. It's hard for [players] to go 20-some plays in a row, and then to tackle like we did ... not good.
"But like our eight victories this season, we have to put it all in the past. It's not going to matter when we take the field."
It's clear that Smith, in his ninth season, takes an active interest in keeping that defense fresh as star linebackers Urlacher (34) and Lance Briggs (31), defensive ends Julius Peppers (32) and Israel Idonije (32) and cornerback Charles Tillman (31) get older. Although the Bears made a key off-season trade for wide receiver Brandon Marshall (sending two third-round picks to Miami), Smith picked defensive end Shea McClellin in the first round (17th overall) when it seemed that offense could have been a draft priority. McClellin, a situational player, has three sacks but only six tackles overall.
Strong-side linebacker Nick Roach is taking over for Urlacher in the middle.
"That defense has been together for a long time, and they have some guys that know it just as well as Brian does," Bears quarterback Jay Cutler said. "He's a big loss, but it's a good group."
Smith says he has turned his attention away from the past four games and toward the task of slowing Adrian Peterson, the NFL rushing leader. Peterson has six consecutive 100-yard rushing efforts, but his 108 yards against Chicago two weeks ago was the low mark in that streak. With the Vikings' passing offense ranked last in the NFL, stopping Peterson is priority one.
"You need to be 'gap sound,' and I'm talking about wherever you are supposed to be, you need to be there," Smith said. "We always preach about playing hard, but you know that he's going to, whatever he has, he's going to come with it every snap."
The Vikings (6-6) have proclaimed this a "must-win" week, but Smith, two games ahead in the standings, has gone a step further.
"We feel like we need to win out," Smith said. "And in order to win out, it's about this next game. We need to do whatever we can to win the game."