The Chicago Bears are having fun while looking a lot like the team that won a Super Bowl a generation earlier.

Off to their best start since 1986, the Bears put their unbeaten record on the line Monday night when they meet Matt Leinart and the Arizona Cardinals at University of Phoenix Stadium.

Chicago (5-0) has lost four consecutive Monday night games, but has won four of its last five meetings against Arizona.

With a 40-7 rout of Buffalo last Sunday, the Bears maintained their season-long domination on both sides of the ball. Chicago is averaging 31.2 points while giving up just 7.2 points per game to lead the league in both categories.

The Bears scored the first five times they touched the ball en route to a 27-0 halftime lead, and came within 66 seconds of posting their first home shutout since 1993.

"That was a fun game," said Rex Grossman, who sat out the fourth quarter after going 15-of-27 for 182 yards with two touchdown passes. "Anytime you execute like that - offense, defense, special teams - anytime you play like that, it's so much fun."

In a career that had been marked by season-ending injuries, Grossman finally is emerging as one of the league's best young passers. Named the NFC offensive player of the month for September by the NFL, he's completed 61.2 percent of his passes (93 of 152) for 1,243 yards,

His 10 TD passes are second in the league behind the 11 thrown by Philadelphia's Donovan McNabb.

"All your hard work coming together and everyone playing the way they're playing, it's fun to see teammates make a bunch of plays," said Grossman, who is on pace for a team-record 32 scoring passes.

Overall, the defense is allowing 234.6 yards per contest, good for third in the league.

Leinart, the 2004 Heisman Trophy winner making his second career start, knows he's in for a test.

"Oh man, their defensive line is so good," he said. "Their ends disrupt the passing game so much that it takes a lot of pressure off their secondary, and their secondary's very good."

Leinart made a successful debut as a starter in a 23-20 loss to Kansas City last Sunday, completing 22 of 35 passes for 253 yards and two TDs. He also won praise from his teammates for his poise.

"Just like a guy who's been here for years and years," guard Reggie Wells said, "very calm. He came to play ball, and there was no hesitation. "

Playing its first Monday night game since 1999, Arizona (1-4) is trying to avoid losing its fifth straight game. Making things more difficult, Leinart will be without one of his top wide receivers.

Larry Fitzgerald suffered a hamstring injury making a short touchdown catch, and will miss the next 2 to 5 weeks.

"I'd say it will be at least two weeks, two-to-five maybe ... it's hard to say," said Cardinals coach Dennis Green, who's 9-6 in his career on Monday nights. "It's a real strong pull, maybe even a slight tear in there also."

The third overall pick in 2004, Fitzgerald had a breakout season last year when he tied Carolina's Steve Smith for the league lead with 103 receptions. Fitzgerald finished with 1,403 receiving yards - the fourth-highest single-season total in team history - and 10 touchdowns.

This season, Fitzgerald was second on the team with 25 receptions for 336 yards. His two TDs tied Anquan Boldin for the team lead.

Leinart now will lean more on Boldin, who has 28 catches for 336 yards. Bryant Johnson, one of two first-round picks by Arizona in 2003, has just 10 catches but is averaging 22.7 yards per reception.

Running back Edgerrin James, meanwhile, continues to struggle in his first season with the Cardinals, but playing before a national television audience may get him untracked.

A five-time 1,000-yard rusher, he's averaging just 68.6 yards this season but seems to save his best games for Monday nights. In seven career games on Monday, James has rushed for 100 yards five times and scored three touchdowns in a game twice.

The Cardinals are 1-5-1 on Monday nights since 1977.