This much we know: With his bold decision to trade up and draft Mitch Trubisky, Bears GM Ryan Pace has made a Dickensian decision.

It will either be the best of moves, or the worst of moves.

We won’t know, of course, for a while, most likely at least two years.

But while we’re waiting, I want to detail what I consider the worst move the Bears’ front office ever made.

Because I had a front-row seat.

The winner/loser is. . . allowing defensive coordinator George Allen to leave Chicago for the Rams’ head-coaching job in 1966.

Owner/head coach George Halas, who was 71 in 1966 and had first coached the Bears in 1920, would coach two more years before elevating Jim Dooley, who never had a winning season in his four-year coaching career.

Meanwhile, Halas let one of the game’s great coaching minds get away. Before Allen went on to engineer turnarounds with the Rams and Redskins, he presided over the Bears’ 1963 championship defense. And in 1965, while coordinating the Bears’ draft, he selected Dick Butkus and Gale Sayers.

Has anybody ever had a better draft than that?

In 1963, when I was a sixth-grader at Deerfield Grammar School, I became friends with. . . George Allen, the son of the coach. Georgie would later become governor, and then a senator, in Virginia.

But all I knew in 1963 was that this guy knew sports. And he was fun. We would ride bicycles endlessly, which you could do in those days in Deerfield, which was on the edge of north suburban Chicago. There were also scavenger hunts. And Georgie liked practical jokes.

We had a very theatrical home-room teacher, Mrs. Coakley, if I remember right. And so, we put on plays, which suited us. There was one where we were supposed to be tall brothers or something, so we made cardboard trees that came up to our chins. In a holiday gala, we did a play, something like “If Santa Claus came to Moscow.’’ I played the awe-struck Soviet son, and Georgie played the befuddled dad.

If I ever met Georgie’s actual dad, it was only a nodding hello. Being a football coach, Mr. Allen was off doing what football coaches do. Hey, the Bears were winning the NFL championship that year.

I still have a program from the final regular-season home game of that season, a 24-14 win capped by safety Davey Whitsell’s interception for a touchdown. I got to shiver through that game in the East Stands with my Uncle Jule because my Uncle Bernie was smart enough to stay in out of the cold.

If you had told me young George Allen would go on to be a big-time politician back then, I never would have believed it. But he was a fount of good sports knowledge.

He was on the Cassius Clay bandwagon at a time when the media was squarely behind Sonny Liston. He was a huge UCLA basketball guy when the Bruins had won zero national championships, an omission they would correct by the end of that 1963-64 season.

And of course, he was a huge Bears guy.

All these years later, I still wonder how many NFL titles the Bears might have won if Papa Bear Halas had been content to make money and win games by letting George Allen do what he did best.

We’ll never know, but the over/under easily could be three.

To make the Halas decision even more painful, the old man reportedly promised to give Allen the head-coaching job, then stalled. And when Allen finally shopped around and landed the Rams’ job, Papa Bear sued him and won, but quickly allowed Allen to leave, saying he merely wanted to make a point about the validity of contracts.

To recap: Because George Halas, who had coached the Bears for nearly 50 years, wanted two more seasons as head coach, he let a great defensive coach and brilliant talent evaluator get away. And went instead with Jim Dooley, who seemed like a nice man but never had a winning season in his four years as head coach.

We’ll see where Ryan Pace’s 2017 draft stacks up. As I mentioned the other day, I don’t get it. But unlike some rabid fans, I’m going to assume Pace knows something I don’t know until he proves that’s wrong.

Is Pace a talent evaluator extraordinaire? A gridiron Theo Epstein?

Or is he in over his head? A front-office Marc Trestman?

I still can’t get a handle on this bizarre Bears’ draft, which included giving up two third-round picks and a fourth-round pick to move up one slot to get Mitch Trubisky.

With their second-round pick, the Bears snagged Adam Shaheen, a 6-6, 278-pound former basketball player who was a walk-on tight end at Division II tight end from Ashland (Ohio) University.

Meanwhile, Michigan tight end Jake Butt slipped down to the Broncos in the fifth round.

Admittedly, Butt, who suffered a torn ACL in the Orange Bowl, may not be the same go-to guy we knew in the winged helmet.

On the other hand, do you want to bet on a D-II tight end? Or modern medicine?

And then there’s the blocker from Kutztown. And no, that’s not the beginning of a limerick. It’s a fifth-round pick.

The curious draft picks of Pace—which will either be brilliant. Or not.—make me think of the best and worst moves by Chicago teams down through the ages. Because there doesn’t seem to be any middle ground on the Trubisky pick. Especially when you consider that shrewd teams acquire plenty of quality players in the third and fourth rounds.

While we’re waiting for the jury, which figures to be out for two to three years, here are what I consider the all-time worst moves by Chicago teams.

I put letting George Allen get away right there in a hat trick.

The Cubs’ trading of Lou Brock is the most famous no-brainer on the list. I knew it even then, and I was just a kid. I wrote a fan letter to Brock requesting an autographed photo. I only did that one other time, with Cubs lefthander Dick Ellsworth.

Brock never got back to me. He was traded to the Cardinals.

Considering what the Cubs had in 1969 and beyond, they might have traded away a World Series or two.

The final Chicago-Worst-Move? The Blackhawks’ trading of Phil Esposito to Boston in 1967 was right up there—or down there—in terms of worst deals by Chicago teams. That helped the Bruins win two Stanley Cups, while the Blackhawks of that era won none.

But that’s all history. The current event is. . . Where will this Bears draft will stack up?

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