ENGLEWOOD, Colo. -- Three colors were prominent above all others during the one-on-one period Friday: orange, blue … and yellow.

This was the second day that NFL officials joined the three locally-based officials on hand for every practice, and when the wide receivers, tight ends, cornerbacks and safeties began facing each other, flags flew at a dizzying clip.

A day earlier, back judge Scott Helverson, umpire Rich Hall, head linesman Wayne Mackie and side judge Keith Washington explained to media the new emphasis on illegal contact and offensive pass interference. Friday, those standards went into practice.

The WR/CB drills are exactly why the officials are here. CBs can learn what will & will not be called. Better now than in the games. — Andrew Mason (@MaseDenver) August 1, 2014

At one point, officials tossed multiple flags as cornerback Aqib Talib and wide receiver Andre Caldwell dueled. Talib spoke to the officials after the play, and again after the one-on-one matchups ended. There were no hard feelings.

"Yeah, we're just giving them a hard time. It's all in fun, man," said Talib. "The one-on-one drill, it's an offensive drill. We're just giving them a hard time. Just making practice fun. That's all."

During the period, flags flew on several plays, including two of three passes at one point.

"Today they were a little trigger happy, they were calling too many flags, but it's part of the game," safety Rahim Moore said with a laugh. "Sometimes they're going to call flags and you've got to learn to keep your composure. Today, we learned that."

Most important is that the Broncos learn to adjust -- which usually is constant, given how rules tweaks are absorbed into general game play, and the fact that not every official sees illegal contact the same way.

"I think they will be a little more ticky-tack with it earlier in preseason. (That) has been my experience," said Head Coach John Fox. "Then they will kind of regulate it back to some kind of normalcy."

Added Talib: "They always talk about it, but once it's September, and the real games start, it'll probably be regular.

"It'll probably go through preseason and die out. It doesn't matter. It is what it is. We're just going to come out here and play football."

And from playing -- or at least practicing -- Friday, five things stood out.

1. Linebacker Von Miller continues to make incremental progress as he completes his recovery from last December's torn anterior cruciate ligament, adding more team-period repetitions to his workload each day.

But it was his work in the pass rush that was the best sign of his progress. On one of his repetitions, he burst around the right flank and forced pressure on Manning, forcing an incompletion.

Miller is lighter and sleeker, even with a bulky brace on his right knee.

"I can't really put a percentage on it. I mean, I feel good," he said.

The knee is not my issue when I'm out there. It's just getting back into the mix, connecting the mind with the body. … and getting that reaction time down."

Miller's quickness off the snap and his acceleration into the backfield around the blockers set him apart two years ago. He's not back to that point yet, but the glimpses of brilliance -- like in that instance Friday morning -- offer the Broncos hope that he'll get there.

2. A rookie steps up:

Lamin Barrow is improving daily. Doing a much better job of filling gaps, reading the blockers setting up a run. — Andrew Mason (@MaseDenver) August 1, 2014

Barrow also forced a fumble near the goal line, stripping the football from tight end Virgil Green, allowing Brandon Marshall to recover.

The competition at middle linebacker is one of the most fascinating of training camp. The first opportunity on the No. 1 defense went to Nate Irving, who briefly had the job in training camp last year, and ended up working at strong-side linebacker. Irving has had a "real nice camp," said Defenisve Coordinator Jack Del Rio.

But Barrow is coming on strong. When training camp began, he got caught up in traffic, and wasn't filling gaps like some of the Broncos' other linebackers. He is now.

"He's getting better every day," said Del Rio. "If you looked at the first day of practice and you looked at today, you'd go 'Wow, doesn't even look like the same guy.' He's progressing, and we just have to see how far we can bring him."

The Broncos drafted Barrow hoping he could push at middle linebacker. So far, so good.

3. At times, Bradley Roby's first NFL training camp has been a humbling learning experience. But the first-round cornerback is starting to learn from his struggles, and responded with arguably his best practice Friday morning. His signature play came when he broke up a pass from Manning to Sanders, who was running a slant pattern. He also made a strong open-field tackle on Sanders, preventing the quick receiver from turning upfield for yardage after the catch.

Roby has looked quicker the last couple of days, as though the NFL game is starting to slow down for him. His reaction time is quicker, and he's trusting himself enough to be more aggressive at the line of scrimmage, which plays into his strengths.

4. Sanders did make plays against Roby and other cornerbacks, and had perhaps the single best play of the day, running a deep out pattern and hauling in a perfectly placed pass near the left sideline inside the 5-yard-line, beating Kayvon Webster in coverage.

There was little that Webster could have done to prevent the play. He had tight coverage, giving Sanders little separation. He was using the sideline as another defender. It was simply a gorgeous throw and an outstanding, lunging catch for Sanders, who was active Friday.

5. Louis Young's groin strain has created more opportunities for other cornerbacks fighting to get a toe-hold on a roster spot. Fellow undrafted rookie Jordan Sullen has taken advantage, and turned in his best day, breaking up a deep pass from Manning to Cody Latimer in one-on-one drills and later doing the same on a long pass attempt from Zac Dysert to Isaiah Burse in a team period.

The team-period play revealed Sullen's adaptability. Sullen read the arc of Dysert's pass, which was slightly underthrown and had too much air on it. Sullen was moving stride for stride with Burse, but he adjusted his read on the football and prevented the long completion.

The play of defensive backs like Sullen only underscores a dominant theme of camp: the Broncos' above-average depth. The Broncos can only keep 61 players between the primary roster and the practice squad, but more than that should have a place somewhere in the league this year.

"It's only going to make us better as individuals and as a unit," said safety David Bruton. "Guys who won't make it here, they'll have great experience, and a great mindset, they'll make it somewhere else or some other team will pick them up.

"Nobody in our secondary should be feared that they won't have a job next year. Everybody is a great player, everybody has the potential to do something no matter where they land."