As Mark Perry did a head count, his head started spinning.

The TCU safety and former CU stopper committed out of Rancho Cucamonga (Calif.) High School to then-Buffs coach Mike MacIntyre in July 2018. From that point until Christmas 2021, CU went through two different strength-and-conditioning coaches, three different safeties coaches and three different head coaches — and a fourth, if you count interim Kurt Roper, who lost at Cal in November 2018 after MacIntyre had been let go.

“When you look at it, most of the guys that ended up leaving, a lot of us had been through (transitions) — while we were at CU, most of us had played for three different head coaches,” said Perry, who’s starting at strong safety against the Buffs on Friday night at Folsom Field, a place he’d called home for the previous four summers.

“I can say it wasn’t a coincidence, that when you break down the people who left (the program), they were all recruited by a different head coach or a different coaching staff. It’s (easy) to say you commit to the school, but at the end of the day, it’s the people inside the building that make the experience.”

As of last February, the typical Power 5 program saw an average of 12.8 departures via the transfer portal, according to 247 Sports.com, a wrinkle that allows players to switch schools once during their collegiate tenures without losing a season of eligibility.

By Feb. 20, 2022, the Buffs had lost 22 players to the portal — tied with Maryland for the most of any major college football program.

And it wasn’t just the quantity that was felt by stunned CU fans. It was the quality. The Buffs have to replace their top rusher (Jarek Broussard, now at Michigan State), their top wide receiver (Brenden Rice, now at USC), their top safety (Perry, whose three picks last fall led the team) and top cornerback (Christian Gonzalez, now at Oregon).

“There were expectations from coaches when guys were recruited here from other (staffs), about what they thought they would be, and it didn’t turn out that way,” said coach Karl Dorrell, who’s opening up his third season.

“So I think (that) is part of that argument. But, you know, we’re happy to be in the position that we’re in right now. Sometimes you have to go through the fire to really refine yourself to be in a type of program (with) expectations and meet those expectations. I think that’s where we are right now. It just took some time to weed out (dissent) and get some guys that are committed to playing for this great university.”

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As the Buffs open the season against Perry and his new teammates, CU finds itself with the lowest percentage of returning lettermen from 2021 (57.3%) of any program in the Pac-12, and the 10th fewest among all 131 FBS programs. (CSU, which went through a coaching change last December, ranks No. 130, with only 51% of its ’21 lettermen coming back.)

While Perry’s quick return — in another uniform — might be happenstance, the reasons a handful of ex-Buffs gave The Denver Post this summer for their departures from the football program, via independent interviews, fell into a similar pattern. And a pattern that often came back to one word: Instability.

While they enjoyed Boulder and, for the most part, their experiences at CU, there was a growing frustration over the churn of new coaches, new faces, and the overall feeling of a lack of control of their respective football destinies. Especially following the short tenure of former coach Mel Tucker, who left the program in February 2020 after just 14 months to take the same role at Michigan State.

“When I was there, I went through three different staff changes,” said wideout Dimitri Stanley, the former Cherry Creek star who entered the portal last January and chose Iowa State. “So I just felt that if I was going to get a new staff, it might as well be somewhere where I can kind of pick, instead of being kind of given whatever (coaches) CU decided (it) wanted to bring in.”

Of the Buffs players who entered the portal, five were, like Stanley, wideouts — a position group that had been largely recruited and coached by former offensive coordinator Darin Chiaverini, a CU alum who was fired by Dorrell last November with a year left on his contract.

“I can’t really speak on anybody else’s reasoning besides my own,” Stanley said. “I know everybody that has left, loves the decision that they’ve made and is as happy (as), or is much happier, honestly, than when they were at Colorado. And it just makes me happy to hear that, to know they’re all doing well.”

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Stanley is listed as a co-starter on the Cyclones’ depth chart for their season opener Saturday against Southeast Missouri. Another former Buff, offensive lineman Chance Lytle, is also listed as a co-starter at guard for his new program, Duke.

“In a lot of ways, it’s really different (here), but in so many ways it is very similar to my experience at CU,” Lytle told The Post. “I went through three head coaches. I went through, man, I don’t know how many offensive line coaches.

“So I kind of went through the whole rebuild process multiple times already. And since (the Blue Devils) brought in coach (Mike) Elko (last December) and they brought in an entirely new staff and they’re rebuilding a lot of what they had going here … the guys here, they had the same staff for a long time, they had no experience with a rebuild. So when I came in, it wasn’t anything new to me.”

After graduating from CU last December with a dual degree in music/voice performance and psychology, Lytle is currently pursuing a master’s at Duke’s Fuqua School of Business. He said the chance to pursue a post-graduate degree in a different program also factored into his decision to leave Boulder.

“I really was kind of flipping back and forth,” Lytle recalled. “I was hearing a lot of different reasons (for guys leaving), some (that were) really valid, some that I didn’t agree with. The one thing that I definitely agree with (Perry) on is, that a lot of older guys, we’d been through a lot — we had cried and bled and sweat together, and we stuck together, no matter (how many) coaches that came through.

“You flew through so many position coaches, coordinators, head coaches — and that’s exhausting on a team that’s really trying to stay together and trying to create a really powerful, strong culture as a group. When I came in (to CU) as a freshman (redshirting in 2017), I spoke to Colby Pursell and I remember talking to him and saying, ‘You know, the culture here, it’s not really where I think it should be.’ I felt like my high school team had a better culture at the time. I’d just kind of expected something a little bit different.

“I talked to Colby, and I was like, ‘We need to change this when we’re the older guys. We’ve got to be different.’ And we really tried to adhere to that …

“And it was exhausting, having a lot of different coaches come in with their own philosophies, their own thought processes on how a team should be run. And eventually, it came to the point where was I like, ‘The only people that we have are each other.’ … I didn’t feel that I had a lot of control over what was going on.”

On Friday, a new-look CU will have a different No. 1 strong safety in sophomore Trevor Woods. But the Buffs, ironically, will feature the same safeties coach — assistant Brett Maxie, who held the position a year ago, one of only three Dorrell assistants still in the same role in which they served last fall.

It’s Perry, strangely, who’ll look different. A purple visage amongst a sea of gold and black.

“When you battle against guys every day, you get to know their tendencies, what kind of guy he is,” the Horned Frogs safety noted.

“I think it’s pretty big for me, being able to go back up there and play somewhere I’ve been for three years, somewhere I’m really familiar with, with people I’m really familiar with. People I still call my brothers.”