The secret to winning at Michigan? Two words, CSU faithful: Party pants.

“Summer of ’84, we’re on the coast of Spain and there’s this flea market right off the beach,” Hugh Millen, the former Broncos quarterback and father of current Rams signal-caller Clay Millen, told me earlier this week.

“I’m 20 years old and I see these pants — they’re the most hideous pants, vertical-striped pants, like the Indiana basketball warm-ups. Only instead of red and white, the stripes are gray and peach and teal. Just hideous. So I called them my party pants.”

Fast forward to September of ‘84, and to the elder Millen’s road debut for the Washington Huskies. The destination: Michigan Stadium — the same spot where son Clay, four decades later, is slated to make his first collegiate start Saturday for coach Jay Norvell’s Rams.

Anyway, back to the pants. As Hugh starts packing for his maiden voyage to the Big House, dude starts thinking ahead. Kind of.

“I know (when) we’re gonna fly back and I know exactly where I’m gonna go right after the Michigan game,” the elder Millen continued. “So I’m like, ‘I’m bringing the party pants, because if we win that game, I’m wearing those party pants home.’

“Then right as I’m about to pack the party pants, (I think), ‘Well, what if we lose? I can’t be wearing party pants on the plane if we lose.’”

Out went the party pants. In went the khakis.

“And I walk out, all the way to where (my) car was parked … and I stopped and looked back at the front door. And I walked back into the house and took out the khakis out of the suitcase. I’m like, ‘I’m wearing the party pants. And that’s it.’”

No. 16 Washington 20, then-No. 3 Michigan 11.

Dress for success, kid. Even if you’re a 30-point underdog.

“I (told Clay), ‘Look, they’re going to make plays,’” the elder Millen said of his son’s CSU initiation vs. the eighth-ranked Wolverines. “’And adversity will hit in the game … (just) don’t let a bad play ruin the next play. Or ruin the next five plays. One bad play only ruins one play, as long as your mind is right.’”

Saturday’s turned into a family affair for the Millen clan. Hugh is one of only four Pac-12/Pac-10 quarterbacks over the last 40 years — CU wasn’t part of the league when Kordell Stewart launched his Miracle in ‘94 — to ever start and win a game at the Big House. And Clay, who’ll throw passes against the Wolverines while being thrown to the wolves, is the grandson of a Michigan Man.

Hugh’s father — also named Hugh — was a Wolverines alum. Grandpa bled so much Maize and Blue, in fact, that he used to buy the annual Street & Smith’s college football magazine, then add up the weights of the respective offensive linemen at Michigan in order to compare their numbers to those of the hated Ohio State Buckeyes.

“I said to him later, ‘Dad, in NFL training camps, there are 20 linemen that go to camp,’” the younger Hugh, who backed up John Elway on the ’94 and ’95 Broncos, recalled with a chuckle. “’Ten go home. And the 10 that go home are just as big as the 10 that stay.’ It’s the feet (with linemen), it’s not the size.”

When Clay earlier this year queried Hugh about the size — Michigan Stadium seats 107,601, most of any FBS edifice — of the crowd he’ll be up against, Dad countered:

“First of all, it’s just noise. Drive around in your car and crank the radio as loud as you can, the top volume. Now let me ask you, ‘Is that preventing you from driving your car?’”

It wasn’t.

“See, you can still drive,” the elder Millen continued. “You can still put on your blinkers. You can still accelerate. You can still come to a stop. It’s just noise. There might be (around) 107,000 people in the stands, but on the field, it’s still 11-on-11.”

And nothing takes a home crowd out of a game like a double-digit deficit they never saw coming. Dad’s Huskies forged a 17-3 lead at the Big House not long after halftime when Hugh hit longtime friend and former high-school teammate Mark Pattison for a 73-yard score.

After the game, Hugh, who’d grown up a Wolverines fan, made a point to shake hands with Michigan coach Bo Schembechler.

“I always wanted to play for you,” the elder Millen told the Wolverines icon.

Schembechler, ears steaming, didn’t say a darned thing.

“He just kept on moving,” Millen recalled.

The Huskies’ defense, meanwhile, gave the Michigan quarterback absolute fits. Much to the chagrin of the Maize-and-Blue masses, the QB in the winged helmet managed to complete just 17 of his 37 throws.

That quarterback’s name?

Jim Harbaugh, the Wolverines’ current coach.

Ah, the plot. It thickens.

“My kids, they kind of have just a cursory knowledge of the Michigan thing,” Hugh said. “But Clay definitely knows how important (the Wolverines are) to his grandpa. And he knows how important it was to me.”

He also knows that the Wolverines, four-touchdown favorites, put their party pants on the same way the Rams do. One leg at a time.