Analyzing the underachieving Green Bay Packers of 2018 brings to mind William Goldman’s famous quote about Hollywood.

Goldman was an all-time great scriptwriter who authored, among other films, “Butch Cassidy and the Sundance Kid,” “All the President’s Men,” “Marathon Man” and “The Princess Bride.”

About the movie industry, Goldman once said: “Nobody knows anything. … Every time out it’s a guess, and if you’re lucky, an educated one.”

That’s probably true in many walks of life, and so it is with the Aaron Rodgers-Mike McCarthy saga this season.

What exactly is the problem?

It’s that McCarthy’s scheme is outdated and stale. It’s that Rodgers relies too much on improvisation. It’s that his rookie receivers don’t know how to get open when he improvises.

It’s that McCarthy can’t get in a play-calling rhythm because Rodgers won’t run the plays he calls. It’s that McCarthy asks Rodgers for plays he likes, then won’t call them.

It’s that McCarthy overly relies on analytics and emphasizes throwing downfield rather than taking checkdowns. It’s that Rodgers is focused on making the special play and missing the easy throw underneath.

It’s that Rodgers is too risk averse. It’s that his accuracy has slipped because he’s falling back on his arm talent rather than fundamentals.

It’s that McCarthy is too bullheaded to stay with Aaron Jones in the run game, or to listen to his best assistant coaches. It’s that Rodgers is changing too many runs to passes at the line of scrimmage. It’s that McCarthy parted with a quarterbacks coach Rodgers’ liked (Alex Van Pelt, whose contract ran out last year). It’s that Rodgers’ body language is bad.

No doubt you can find an expert around the league — a coach, a scout, a pundit who played or coached or scouted — to back up any of those critiques. And there’s probably some truth to many of them, maybe even most.

But it’s also just noise.

About the only thing that’s certain in all this is that the chemistry between the Packers quarterback and coach is gone. They had it once upon a time, but no more. So it’s hard to see how anything McCarthy does the rest of this season can save his job after 13 years. Maybe a deep, deep playoff run would do it, but really, what are the chances of that?

If I’ve learned anything covering the NFL for 26 years, it’s that however important you think quarterback play is, it’s more important than that.

That makes the relationship between the quarterback and coach (or whoever’s running the offense) paramount. They don’t have to be friends. They can get mad as hell at each other a lot. They can even be sick of each other.

But in the end, there still has to be a sense of trust, faith and collaboration to hold things together, and anyone who has observed the Packers this year can see there’s just not enough between Rodgers and McCarthy. This has become a bad marriage that’s filtered through the rest of the house. It has run its course.

At this point, it doesn’t matter who’s more to blame. All that matters is Rodgers isn’t buying what McCarthy is selling and isn't playing anywhere near an MVP level. That’s why the Packers are 4-6-1.

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Instead of a creative push and pull, it’s like Rodgers and McCarthy are running two different offenses. That’s a house divided against itself.

Contrast their partnership with the tight, energetic collaboration between Drew Brees and Sean Payton in New Orleans, which Peter King of NBC Sports chronicled when he embedded with the Saints the night before a game a couple of weeks ago.

“The evolution from where we were, call it 13 years ago, when we all first got here in ’06 to now, is pretty amazing,” Brees told King. “It’s an exciting process.”

Then there’s this from Monday Night Football commentator Booger McFarland, who took part in the broadcast crew’s production meetings, conducted separately with Rodgers and McCarthy, before the Packers’ Monday night game against San Francisco in October.

“Maybe it’s their personalities,” McFarland told Kalyn Kahler of MMQB.com, “but to me, I find it very (unusual) that you get two people who (say they) really enjoy working together and enjoy being around each other — but you can’t sense or see that. I didn’t sense that from either Aaron or coach.”

Barring the miracle finish, it’s quite apparent one of them will have to go, and it’s not going to be the quarterback. His new contract alone makes parting with him prohibitive. If the Packers moved him in the offseason, they’d be eating about $66.9 million in cash plus $32.9 million in 2019 cap room. Also, good quarterbacks are harder to find than good coaches.

To that point, I see and hear plenty of people trashing McCarthy and find it laughable. Of course he deserves criticism, and we’ve all taken our shots, more this year than ever. Every NFL coach, even the great Bill Belichick, makes mistakes, lots of them. And maybe it’s time for McCarthy and the Packers to start anew regardless.

But how many of these coaches are really any better than the others? Think about it.

Last year, Eagles coach Doug Pederson was a genius. This year, he’s 5-6.

Last year, 49ers coach Kyle Shanahan was the toast of the NFL when he went 5-0 to close the season with Jimmy Garoppolo at quarterback. This year, without Garoppolo, he’s 2-9.

I’m sure the Rams' Sean McVay is a fine coach and maybe over time will prove to be special. He has certainly done good work with Jared Goff. But besides a promising quarterback, McVay also has the best running back and best defensive player in the game. That’s a pretty good starting point.

The Chiefs' Andy Reid is suddenly all that, too. Funny how he wasn’t so innovative when Alex Smith was his quarterback. But with the incredibly talented Patrick Mahomes and a couple of special players around him, Reid suddenly is a cutting-edge offensive mind. Just a reminder, this is a guy who in his 20 seasons as an NFL coach hasn’t won a Super Bowl.

That’s not a shot at Reid. The point is, there’s probably not that much difference between many of the good coaches in this league.

Still, the McCarthy-Rodgers marriage has run its course, that much is clear. It’s hard to see how Packers CEO Mark Murphy and general manager Brian Gutekunst can conclude otherwise.