Bears quarterback Jay Cutler is irreplaceable.
Not on the field. Injuries will keep him out of Sunday's game against the Ravens, and Josh McCown is expected to be capable as a fill-in.
Off the field is something else. Nobody could be as interesting as Cutler has been during his five years with the Bears.
With Cutler there's always intrigue just around the corner, drama in every nook of Halas Hall, and suspense in every approaching cranny of the season.
The guy is at the center of everything, as all quarterbacks are, only in his case more compellingly than most.
Cutler is one of the most complicated and complicating athletes in recent Chicago sports history. Name another who fits that description more: Sammy Sosa perhaps; Frank Thomas perhaps; Patrick Kane for a while perhaps.
But this Cutler thing is a week-to-week, season-to-season saga. Bless him for that. Local media are obligated to provide Bears coverage 24/7, and Cutler helps fill airwaves and column inches.
If Cutler isn't making smart coaches dumb, he's making strong coaches weak or good coaches worse.
Take current Bears head coach Marc Trestman.
Sunday he said Cutler was healthy enough and playing well enough to stay on the field. Monday morning on WBBM-AM he said maybe he should have taken his quarterback out of the game earlier. Monday afternoon he said he had no regrets over leaving the gimpy QB in so long. Today, who knows?
Trestman's confusion pours fuel on the ongoing debate over whether Cutler is a franchise quarterback or franchise killer. This has been going on during his eight NFL seasons and five here with the Bears.
Cutler already has received millions of dollars in salary, married a beautiful reality-TV star and been given a weekly radio gig.
These usually are rewards for a quarterback who has won at least one Super Bowl.
Jay Cutler has won one playoff game.
The Bears have invested salary-cap space, responsibility and power in Cutler. They have given him quarterback coaches and wide receivers he wants and now a head coach who fits his needs.
Excuses have been manufactured for Cutler. Apologists inside and outside Halas Hall have lent him support. He's the man.
"He's our starting quarterback," Trestman said Monday afternoon in explaining why he kept Cutler in the Lions' game. "He's our leader."
The question is whether Cutler is qualified to be a quarterback because he's a leader or a leader because he's a quarterback.
Either way Trestman added, "We want him to be in there. He wants to be in there."
Never mind that Cutler has had trouble staying healthy, trouble maintaining reliable mechanics and trouble becoming everything he's expected to be.
Cutler's remarkable physical tools -- arm strength, mobility and overall athletic ability -- continue to tease and tantalize. However, something always interferes with Cutler's potential to join Tom Brady, Aaron Rodgers, Drew Brees and Peyton Manning among the NFL's elite quarterbacks.
Now it's a high ankle sprain on top of -- or underneath -- a recovering torn groin muscle. Previously it was inferior coaching or an unworthy supporting cast or this or that or this and that or whatever and everything else.
So here the Bears are, at the same place they were five years ago, still evaluating what Cutler is and still hoping he will be what they need him to be.
Seven games remain in this Bears season for Jay Cutler to prove what he wasn't able to prove during his first seven seasons in the NFL.
As usual, he'll find a way to make the process interesting.