ENGLEWOOD — What is the biggest growth for Broncos quarterback Bo Nix from the start of training camp to now?

“I think it’s just comfort level with just the operation,” offensive coordinator Joe Lombardi said Thursday, following the 12th practice with fans at Broncos Park. “It’s just getting the huddle calls, some of the checks at the line of scrimmage. Just the more you see that, the better you get. He’s just getting more comfortable.”

There is still no clarity on which quarterback will start in Sunday’s preseason opener at the Colts. Jarrett Stidham and Nix continue to rotate first-team practice repetitions with Zach Wilson typically leading the third team. But it’s difficult to ignore the buzz surrounding Nix.

Lombardi added to a growing list of glowing endorsements for the 24-year-old rookie quarterback.

“He’s everything that you hope for, just with his intelligence and the way he studies and prepares,” Lombardi said of Nix. “When you give him a play, and it’s new, and the defense has a new install, there’s not as much confidence when he gets it. … Then, after a couple of days, when you’re running the same plays, you just feel like he’s a veteran.”

Lombardi explained the message for all three quarterbacks in Indianapolis on Sunday.

“Just a clean operation. Just playing good football with the situation that’s presented to them,” Lombardi said. “Make good decisions and take the plays that are there. If we call a bad play, make sure nothing bad happens. Just operate well.”

Sterns waived again

Safety Caden Sterns — a fifth-round draft pick (‘21) released Monday by the Broncos — is on the move once again.

The Panthers initially picked him up on waivers. But they placed Sterns on waivers Thursday after a failed physical, the team reported.

Sterns tore his patella tendon, a season-ending injury, in Week 1 last season. The Broncos reported that Sterns passed his physical on July 27. Coach Sean Payton said at the time: “It’s nice to see him back on the field. It took a while, so we just have to be real measured and smart with his acclimation back.”

Secondary depth

Young players in the secondary are being tested in training camp due to injuries. The Broncos are currently without safeties Brandon Jones (hamstring), Delarrin Turner-Yell (ACL) and cornerback Levi Wallace (hamstring).

“It’s not good for those guys obviously and good for us overall, but it’s good for our young guys to get reps,” defensive coordinator Vance Joseph said. “Obviously there are injuries during the season, so starting now with guys just stepping in and the standard staying the same is important. Those two guys are smart guys and experienced guys. Missing the physical reps are obviously a problem, but (they’ll be) just fine.”

Releasing Sterns, specifically, should increase opportunity for young safeties like Devon Key and JL Skinner.

“It’s been fun to watch them both grow,” Joseph said. “They both are taking strides with making calls.”

Briefly

Lombardi said the staff planned to discuss starter snaps Thursday afternoon for the preseason opener. … Stidham’s birthday was on Thursday. He turned 28. … Special teams coordinator Ben Kotwica discussed the balance between practice for new kickoff rules in preseason, and not giving away their regular season plans. Kotwica said: “On Sunday, we really want to see who can block, who’s good at block destruction and who can tackle. The evaluation process is still a huge part of it. But you have to also balance that with the new play.”