The moment of truth for Grossman, Lovie

ST. LOUIS -- This is no time for cutesy, little Rex puns, now numbering in double digits and making me nauseous. Rather, we've arrived at a firm, inevitable, undeniable ultimatum. If Rex Grossman stumbles again tonight, for the sixth time in eight games, amid the climate-controlled comfort of a dome against the wet-sponge defense of the Rams, it's so much more than Train Rex and Gross, Man.

He's out.

As in, done, useless, past tense, clipboard, another spectator with a front-row seat and ballcap as Brian Griese tries to save the Bears from another tease-and-fade season. And it's quite likely that once the brain trust makes the change, it will remain permanent through the playoffs, which means Grossman would be subjected to offseason doubts about whether he's qualified to be the long-term starter. Basically, his career and reputation are on the line in the Edward Jones Dome --named for an investment firm, fittingly enough -- as football America wonders why a team with so many strengths would continue allowing a shaky quarterback to sabotage a season.

At least Rex realizes his NFL life is flashing before his eyes. ''Definitely, it's getting to the point where it's pretty critical that I start the way I'm capable of playing,'' he said.

Of course, the Bears face other daunting issues that make those frantic September calls to Super Bowl travel agents seem so silly. Here in the gray of a gathering winter, they also must deal with the devastating loss of Tommie Harris, likely out the rest of the season with a serious hamstring problem and sprained left knee. Already vulnerable against the run since safety Mike Brown was lost to torn foot ligaments in October, the defense now is depleted by the loss of an interior force. Normally, Brian Urlacher isn't fazed by much. This fazes him.

''It's going to be tough to replace him. It's going to be like Mike Brown -- you're not going to replace him,'' Urlacher said.

''No one in the league has a player like Tommie Harris,'' Lovie Smith said. ''So now I see us being like everyone else. Everyone else has played without a dominant player like that. Does it change the dynamics of our team, the defensive line? Yes, for sure.''

People would feel better about the crater in the defensive trenches if the quarterback was at least decent. Like everyone beyond Smith, Jerry Angelo, Ron Turner and Rex's immediate friends and family members, I would have switched to Griese long ago. The Bears have too much at stake, in a still-winnable NFC, to waste a rare Super Bowl opportunity on Grossman's development. While a shrewd Bill Parcells reversed the Dallas Cowboys' arrow upward, with a bullet, after benching Drew Bledsoe for Tony Romo, Smith has stubbornly stuck by Grossman as the Chicago media neurotically splash 24/7 coverage of ''REX'' like he's some three-initialed contagious disease. Might that be the difference in who wins the NFC title? In Jacksonville, the Jaguars have been markedly better since coach Jack Del Rio committed to David Garrard at QB. All you need to know is that Grossman has posted four passer ratings below 40 this year -- no other league passer has more than two -- and that the Bears somehow wound up 2-2 in those games thanks to the defense and miracle returner Devin Hester. You almost wish they'd have lost all four to force a change earlier, giving Griese more time to acclimate.

What should bother the Bears, even more than Grossman's 14 interceptions and three lost fumbles over the last seven games, is his psyche. It's shaken, all but shot. After posting a 1.3 passer rating against Minnesota, he said nothing could rattle his confidence. But did you hear his hazy ramblings the other day?

''I'm just so confused why I do some of the things I do,'' Grossman said. ''It doesn't make any sense to me. It's, ''All right, what is making me do these things?'''

It's nice to see him seeking advice from many people, including his father. But Grossman, I'm afraid, has the classic symptoms of a head case. ''Sometimes you analyze things so much, you overthink things. Talking to my dad, you just have to go play football: It's a game, relax, go play football,'' he said. ''I know this offense so well, I study it so much, sometimes I think myself out of things.''

No one has time for a wavering mind, not with postseason games ahead and anyone born during the 1985 super-season now of drinking age. Nor do I think Grossman has to simply win the game. Tonight is about determining if there's a chance, even the slightest, that he can efficiently pilot this offense in a playoff context. The temptation will be to run the ball against the league's worst run defense, which has allowed 100-yard games to nine backs this season. This would be a fine night to feature Cedric Benson, who has quietly -- on the field, anyway -- been averaging five and six yards a pop and is looking like the $17 million-bonus runner who can be leaned on in cold weather. As Rams defensive end Leonard Little said, noting the holes in his team's scheme and Grossman's problems: ''We're expecting them to run the ball. We're expecting them to run the ball on all three downs, maybe four downs.''

But it's also vital to let Rex throw frequently and see if he can develop any kind of rhythm, as he did in the second half against the Giants in his last prime-time night gig. You don't want him having a limp winning performance, as he did against the Jets, and creating false security. He needs a mistake-free, two-touchdown, commanding performance before I begin to think this can work out. The last thing he needs: A game like Mike Tomczak had in 1987 on a Monday night, when he was an interception machine and became known as LOTTO -- as in, Pick 4. As memory serves, that was the game Ditka threw his gum wad.

Is Rex capable of a Pick 6?

Actually, no, because he would be replaced long before then. Griese has been getting more snaps in practice and is prepared to give the Bears more efficiency, fewer errors and a better shot of letting the defense and Hester win the NFC. I'm not calling him a savior, recalling some of his own wobbly tendencies in the past. But this is a man who has matured markedly since his Denver days, when he fought personal problems, and will bring stability and poise that Grossman lacks. I'm not sure Griese can reach a Super Bowl, but I'd rather watch him try than oversee a Grossman flop.

''We all want to be playing, but there's only one job out there,'' Griese said. ''I have one job and that's to go out and prepare. It's my job to be ready if called upon.''

Get ready.

Jay Mariotti is a regular on ''Around the Horn'' at 4 p.m. on ESPN. Send e-mail to inbox@suntimes.com with name, hometown and daytime phone number (letters run Sunday).