When the Broncos faced San Francisco in a joint practice last month, there were a trio of Super Bowl-winning coaches who watched.

There, of course, was Denver coach Sean Payton, who won a ring with New Orleans in the 2009 season. Standing between the two fields on that Aug. 7 morning in Santa Clara, Calif., was Mike Shanahan, who won Super Bowls with the Broncos in the 1997 and 1998 seasons and is the son of 49ers coach Kyle Shananan. And watching the practice on video later on was Gary Kubiak, who won a Super Bowl with Denver in the 2015 season and is the son of 49ers offensive coordinator Klay Kubiak.

Shanahan and Kubiak both spent plenty of time looking at second-year Broncos quarterback Bo Nix.

“I just wanted to see what type of athlete he was by the way he played,’’ said Shanahan, Denver’s head coach from 1995-2008. “I could see very quickly his arm strength. … You could see he’s very comfortable throwing off balance and making big throws down the field.”

Kubiak played quarterback for the Broncos from 1983-91. He later was Denver’s head coach from 2015-16.

“The young man was very impressive,’’ Kubiak said about Nix in the joint practice. “He’s extremely well coached. … There’s some things that as a quarterback are really hard to teach and that’s composure and the big one is accuracy. And when I watch him, he dominates in those phases.”

Shanahan last season saw several Broncos games in person and watched others on television at his home in the Denver area. Kubiak watches Broncos games regularly from his ranch in Plantersville, Texas.

Judging from what they saw last season and then in the joint practice, both see improvement in Nix from when he threw for 3,775 yards and 29 touchdowns with 12 interceptions as a rookie after being the No. 12 pick in the draft out of Oregon.

“I think any time you learn an offensive system, it takes time,’’ said Shanahan, who met Nix for the first time at the joint practice. “What he was able to do in his first year was really quite remarkable because he came with a lot of pressure on him without a lot of depth on the football team. And now you can see that he’s got a much better supporting cast on both sides of the ball. … He’s a really impressive person. I just like the way he handles himself both on and off the field and you can see he’s a natural team leader. You can see that the players look at him as a leader. And he processes things very quickly.”

Kubiak said Nix is operating faster than as a rookie.

“I’m a big advocate when I watch offensive football in tempo,’’ Kubiak said. “How fast you huddle, how fast you operate. And just watching him operate, that really stands out. When you watch all these great quarterbacks, there is no standing around.”

Shanahan and Kubiak know plenty about great quarterbacks. Kubiak was a backup on the Broncos to John Elway and Elway later won Super Bowls XXXII and XXXIII under Shanahan. Then Kubiak won Super Bowl 50 with Peyton Manning behind center.

Now Payton, who had Drew Brees as his quarterback when he won Super Bowl XLIV, has talked openly about a belief the Broncos have what it takes this season to make a run at winning it all. That includes their quarterback.

“Sean’s been doing it a very long time, so he knows when he’s got a group that’s very capable (of winning a Super Bowl), but he also understands how darn hard the NFL is,’’ Kubiak said.

Throw in that they have one of the best defenses in the NFL, and Shanahan has no issues with Payton’s touting of the Broncos.

“They’ve got a chance to win the big one, and that’s what their goal is,’’ Shanahan said.

Broncos brass has been talking big about Nix. General manager George Paton recently said, “We feel like we have a franchise quarterback.”

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Payton recently told Yahoo! Sports that Nix has the ability “to be one of the top four or five quarterbacks in the league the next two years.”

Nix seems comfortable with such praise.

“If he believes that, and I know I have a lot of work to do to get there, I don’t want to let that word void,’’ Nix said of Payton’s projection. “I want to give it my best shot at going out there and doing that. … We talk about Super Bowls, talk about winning culture, that helps a lot in being the best that I can be.”

Come Sunday’s opener against Tennessee at Empower Field at Mile High, Nix can start trying to live up to the hype.

“We’re excited to start the season and get to Week 1 and see what happens,’’ he said. “(I’m) very ready, very excited.’’

Nix has come a long way since last year’s opener at Seattle. In a 26-20 loss, he completed 26 of 42 passes for just 138 yards with no touchdowns and two interceptions and had what would be a season-low passer rating of 47.5.

But Nix continued to improve as the season went along. His first win as a starter came in a 26-7 wipeout of Tampa Bay in Week 3, when he threw for 216 yards without a touchdown pass. By Week 11, he threw for 307 yards and four touchdowns in a resounding 38-6 win over Atlanta.

Yes, it was against Kansas City reserves. But Nix saved his best for Week 18, when he completed 26 of 29 passes for a career-high 321 yards and four touchdowns in a 38-0 victory that clinched Denver’s first playoff berth since 2015.

Now there is plenty of talk about how much Nix has improved over the past year.

“He’s out of the huddle a little quicker with the call; maybe he understands the nuances of the play; and has seen the cut ups of it all year and is a little bit more comfortable with the same play from a year ago,’’ Payton said.

Wide receiver Troy Franklin is entering his fourth straight season as Nix’s teammate, having played with him at Oregon from 2022-23 before also coming to Denver.

“I see him as just a more confident guy,’’ Franklin said the difference between Nix in his first and second Broncos season. “He’s talking to all his guys, making sure we know everything and giving us reminders that the ball’s ours when it’s in the air for the receivers.”

Arizona defensive end Calais Campbell, a Denver native and 18-year NFL veteran who grew up a huge Broncos fan and still keeps tabs on the team, spoke of Nix’s continued improvement after the Cardinals faced Denver in an Aug. 14 joint practice at Broncos Park.

“He has what it takes,’’ Campbell said. “He’s poised, made quick decisions. He didn’t hold the ball long at all. I feel like he understands every situation.”

Against the Cardinals, Nix had perhaps his best day of training camp. He threw the ball all over the field to a multitude of receivers.

Of course, Denver’s joint practice the previous week against the 49ers wasn’t too shabby either. A pair of Broncos Super Bowl-winning coaches sure liked what they saw that day.