Exactly one year ago, Garett Bolles was still defined by his mistakes.

On this same date in 2019, he was called for his 12th holding penalty of the season in just 11 games, and his 15th holding infraction in a 13-game stretch dating back to the previous season. The progress he made was undermined by penalties.

Now, he’s defined by nearly flawless play. The next sack he allows this season will be his first, and he is now working on a streak of 18 games without allowing a sack, according to the data compiled by Pro Football Focus.

At danger of being considered a first-round bust, Bolles is now one of the best at his position, a legitimate All-Pro and Pro Bowl candidate.

“The stuff he is doing is Pro Bowl,” running back Phillip Lindsay said after last Sunday’s win over the Miami Dolphins. “He’s having a hellacious year.”

What changed?

It was a commitment to technique.

“I think in the past I just used my athletic ability to get the job done,” Bolles explained, “but I think the more I’ve been in the league, the more I watch film and I watch myself, the more I really dial in on the technical side of things.

“You talk about some of the greatest tackles to play — Joe Thomas, Jonathan Ogden and Joe Staley — those guys were technicians for a reason. They were 10-time Pro Bowlers, Hall of Fame players, first-time [Pro Football Hall of Fame] ballot players because of what they did on the field with their technique.

“To the little things where taking sets barefoot in your kitchen to watching film, watching guys, looking on the outside shoulder, hand movement and hand fights, and things like that — those guys did it and so just hearing from them and hearing their stories, makes me want to just continue to go out there and work on my technique. I take it seriously.”

As the penalties and pressures accumulated in his first three seasons, Bolles reached a point to where he knew he had to change how he attacked his day-to-day work. He had to listen. He had to practice. And he had to study film.

“I just watched film,” he said. “Like I’ve said before, I really think I’ve just watched film over the years and really realized, ‘Hey, why am I continuing to make the same mistakes?’

“I know last year I told you all, ‘I’m not going to change how I play.’ What I meant there is that I’m not going to change my mentality of being a dog out there. I’ll never change that mentality at all. What I did need to change is how I saw things and how I placed my hands and how I moved my feet, how I keep my shoulders and my numbers square for two kick slides or how I take two kick slides, pause, and get on my guy. Those were the things I had to learn, and it took time.”

It also took the influence of offensive-line coach Mike Munchak, who joined the team in 2019 after interviewing for the head-coaching job that went to Vic Fangio.

“[I] talked with Munchak to really figure out what it was, and I figured it out,” Bolles said. “I shouldn’t say I’ve figured it out yet because I still think I have a long way to go, but I still think I’m on the right track of becoming great. That’s what makes me proud of myself and what makes me proud of everyone that’s stepped up with me and given me the love that I needed.”

Love comes in various forms. For Bolles, it came in the form of teaching and critique day-in and day-out.

“[Coach] Munchak and I talk on a regular basis,” Bolles said. “I love that man dearly. I give him all the credit in the world because of what he’s done with me and in such a short amount of time, and it’s really nice to know that I have an o-line coach I can rely on and that I can trust and we can talk man-to-man.”

The results are clear.

Bolles has just four holding penalties in his last 15 regular-season games. After amassing 17 total penalties last year, he has just six this year — three of which came in the game that Munchak had to miss due to COVID-19 protocols.

He is also allowing fewer pressures and sacks than ever before. Among the 82 offensive tackles with at least 150 snaps played this year, Bolles’ pressure rate of one pressure allowed every 48.6 snaps ranks second in the league behind Andrew Whitworth of the Los Angeles Rams, according to pressure data compiled by Pro Football Focus.

Pro Football Focus also credits Bolles with no sacks allowed, making him one of just 13 offensive tackles with at least 150 snaps played with that distinction. (One of the other 12 is right tackle Demar Dotson, whose return to the lineup last Sunday helped the offensive line settle into a groove.)

Thanks to experience, Munchak’s guidance and the emphasis on technique, Bolles finally looks like the first-round talent the Broncos expected him to be when they picked him after just one season starting at the University of Utah.

“When I first got here, I hadn’t played left tackle for a long time so I had to learn by trial and error,” Bolles said. “Once I realized that and once I realized, ‘Hey, look at all the good reps I’m doing,’ and, ‘OK, why am I having 50-50 or 75 bad ones and 20 good ones, why?’ I really had to dial it in in the offseason, watch film, get to the people that helped me in the offseason.”

And to fully grasp how much has changed, all you have to do is compare the thoughts of Broncos coach Vic Fangio.

A day after the Broncos’ ninth game of 2019 — a win over Cleveland in which Bolles committed two penalties in a three-snap span — Fangio said that Bolles “kind of plays with more confidence than you think — and maybe than is warranted.”

Fangio quickly added that in the overall summation of that game, Bolles “didn’t play too bad.” But he noted that there was far more work to do to make the most of Bolles’ skill set.

“It’s our job to maximize and make sure we’re doing everything possible to develop him,” Fangio said then. “If the guy has talent, we want to maximize every opportunity to develop it.”

Just over a year later, Fangio declared that Bolles should receive Pro Bowl consideration.

He’s not defined by his mistakes anymore. He’s defined by the honors that are about to accumulate — and the massive paycheck likely coming at some point in the next two years. He might have to wait until after a year spent playing on the franchise tag to receive it, but one thing is certain: Bolles has become one of the game’s best players at a premium position, and he’s going to be paid like it.