Sunday's 41-21 defeat to the Arizona Cardinals, a game more lopsided than the final score indicated, demonstrated that the 45-10 shellacking in Cincinnati on Oct. 25 was no aberration. The once-proud Bears' defense is staggering as it prepares for Thursday night's game against the 49ers in San Francisco.

The Cardinals scored four touchdowns and two field goals in their first six possessions and didn't punt until 5:38 remained in the third quarter. Three games ago, the Bengals scored six TDs and a field goal in their first seven chances.

"We're not going out and earning our paychecks. We're not doing it," said an emotional defensive end Alex Brown. "I'm sorry. I'm too upset. …. We need to get better."

Added coach Lovie Smith, "We have some soul-searching to do right now."

The Cardinals, who entered the game ranked last in the NFL in rushing, ran for 131 yards in the first half and 182 in the game. They scored TDs on drives of 81, 74, 70 and 86 yards in their first four possessions to take a 31-7 halftime lead. They converted their first eight third-down plays before settling for a field goal on their first possession of the second half. "Third downs have killed us most of the year," Smith said.

The Bears' defense showed a brief spark in the fourth quarter when it intercepted backup quarterback Matt Leinart and then sacked starter Kurt Warner, back in the game, on a three-plays-and-out series. It only raised the question where the intensity had been for the first three quarters.

"For five minutes there, we played like we can. We played like we believed we could win. Why can't we play like that from zero-zero?" Brown said. "We're going to have a lot more of those games these last eight games if we can't figure that out."

Added defensive back Nathan Vasher, "We just can't wait that long to turn it on it."

Defensive tackle Tommie Harris was ejected on the fourth play of the game for punching guard Deuce Lutui in the facemask as the Arizona lineman was on the ground. His absence didn't help, but Harris hasn't played to his old Pro Bowl form and was benched for the Bengals' game after he didn't practice all week because of his chronic knee injury.

After the Bears' consecutive disappointing seasons on defense (ranked 28th in '07 and 21st last year), Smith assumed a larger role this year, including taking over play-calling duties. Season-ending injuries to linebackers Brian Urlacher and Pisa Tinoisamoa have contributed to the problems, but the two recent defensive meltdowns have raised the public criticism of the head coach to levels unheard of in his first five years.

"We're an average team right now, with the potential to do some great things in this second half," Smith said.

Harris, who has apologized for his actions, could be fined and/or suspended by the NFL. Starting defensive backs Charles Tillman and Al Afalava both left Sunday's game with shoulder injuries but could be back for the 49ers.

After Thursday's game, the 4-4 Bears play the Eagles at home and visit the Vikings, who lead the NFC North by three games. Chicago's 2-3 conference record doesn't help its fading wild-card chances, and the players sounded a tone of urgency after the Arizona loss.

"It's a cliché and everybody says it, but play like it's your last down," Brown said. "If we can do that, I think we can right the ship and go in the right direction. If not, we'll be going home soon."

Enlarge By Jonathan Daniel, Getty Images Lovie Smith and the Bears are 4-4 and will travel to San Francisco for a game on Thursday.