He led the team as a coach last season to the Super Bowl 50 Lombardi Trophy. He did it twice as an offensive coordinator for the franchise in the 1990s. On Monday, he retired after 23 seasons as a coach and nine as a player.
But Kubiak's best player, Von Miller, won't forget the legacy he left behind.
"The hardest thing to do in football is lose," Miller wrote for Sports Illustrated's MMQB. "Any coach can stand up in front of a team after a win, crack a joke and say, "See you on Monday." But it takes a real coach with a great understanding of what makes a team click to bring people together after a loss. That's what Gary Kubiak did, and that's who he was."
Kubiak, 55, leaves the game with a 82-75 record as a head coach for the Houston Texans and Broncos.
"He was a leader who was believable, a man of high character who always had a plan," Miller wrote. "He used to assign me what I call side missions—after team meetings he'd pull me aside and tell me what he needed from me that day, whether it was raising the intensity level at practice or heightening the focus on the details. I was excited and proud to be called on."
Miller, the 2015 Super Bowl MVP, is a four-time Pro Bowl pick and two-time First-Team All-Pro. This season, he had 13.5 sacks, 62 tackles, and three forced fumbles.
"And when this season didn't work out as we had hoped, missing the playoffs for the first time in my career, he did the hard things that great coaches do," Miller wrote. "In private, he talked to his players straight up, communicating clearly his expectations and corrections. In public, he took the blame for everything—even things that weren't his fault. Every football team has little pods and little groups that can splinter off when you hit obstacles, but he did a great job of keeping everyone together when the ship felt like it was sinking."
"So I'll keep doing his work, fulfilling the missions he gave me, and I will always remember the trust and respect he had for me from the first day."
The Broncos finished the season 9-7, missing the playoffs for the first time since 2010.
"I gave everything I had to this team the last two seasons, but this year, in particular, has been tough on me," Kubiak said in a statement. "As hard as it is to leave this position, I know that it's the best thing for myself, my family and the Denver Broncos."
"I'm not sure what my future holds, but I know that I'll always consider myself a Bronco," Kubiak said. "This team is in good hands with a lot of outstanding people, and I expect great things ahead for the Denver Broncos."