Chicago ? Lovie Smith doesn’t like to change horses in midstream.

A football coach doesn’t quit on a quarterback as quickly as outsiders do. He tends to be unwilling to do so until a team has been bent like a wishbone and then been bent a little more and is just about to crack.

At that breaking point, a coach is not obstinate to the point of self-destruction. He can’t be. The fate of about 50 other men in the room plus his coaching staff is at stake.

And after what took place Sunday night at Soldier Field, that breaking point has to be at hand.

The vox populi is demanding a replacement for Rex Grossman as the Bears’ quarterback. It has become impossible to defend him. The team’s most thick-skinned and resilient fans have seen enough.

As for those holdouts among us who have advocated restraint, even we are at long last prepared to concede.

Smith would be wise to bite the bullet and give somebody else a shot, precisely the way he did toward the end of the 2005 season when Kyle Orton, even while victorious, was inadequately getting the job done.

He needn’t throw Grossman onto the scrap heap or, in the cliche of the millennium, under the bus.

For unity’s sake as well as common sense’s, however, the time has clearly come for Smith to bend before the Bears break.

When he benched Orton at halftime of a Dec. 18, 2005, game against the Falcons, the quarterback was coming off eight victories in a row before a loss in a Pittsburgh blizzard to a Steelers team that would go on to win the Super Bowl.

Smith’s rationale then: “I felt like we needed a spark.”

He waited until halftime of Week 15 but did so partly because Grossman had to mend from a broken ankle until he was fit to play. Orton was ineffective to the extent that Smith simply couldn’t put it off any more.

Brian Griese is not unfit. He might be “a Band-Aid,” to use John Madden’s description, but isn’t it better to stop the bleeding now than to let it gush?

Orton himself is still on the premises and could rate a shot at relieving Grossman, now that the shoe is on the other foot.

Either way, Smith has the luxury of two backup quarterbacks with NFL starting experience. And he has the dilemma, as he did in 2005, of trying to determine how much inadequacy he can tolerate and how far you bend before it’s too late.

The coach is being coy about his quarterback plans for Week 4, when the Bears will be in Detroit to face a Lions team that could come out of this game with a record of 3-1 to his team’s 1-3.

“Will Rex Grossman start Sunday? Well, our evaluation process is going on right now. If you come out to practice Wednesday, you’ll have a better idea of who will be starting at all positions,” Smith said, sidestepping the question on everyone’s mind Monday.

His team’s bodies are as broken as its spirit.

A game that featured what NBC advertised as “football’s two most popular teams” landed with a thud and ended with Chicago’s fans, three games beyond a Super Bowl, lustily booing their own men.

One man in particular.

Bears fans were not born yesterday. They understand that neither Griese nor Orton is a guaranteed cure-all for what ails their team’s offense.

But when that offense has manufactured a mere two touchdowns in its last 15 quarters of football, including the last three of the Super Bowl, even a blind Bears fan could see that something is very, very wrong.

And something, even if only a Band-Aid, needs to be done about it.