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ENGLEWOOD, Colo. --** There have been plenty of practices this summer with hotter temperatures, but none with hotter tempers, and that's where today's Five Thoughts begins:

Two fights in the last five minutes. One on the sideline. Temperatures rising. — Andrew Mason (@MaseDenver) August 12, 2014

1. The series of skirmishes began when center Will Montgomery and defensive tackle Kevin Vickerson tussled. During the remainder of that team period, the fracases continued. In one donnybrook that began when Duke Ihenacho and Brennan Clay tangled, the fracas went to the sideline, where players had to get out of the way or get involved to break it up.

It was inevitable that Head Coach John Fox would have to speak to regain control of a practice that at times seemed to straddle the line between order and chaos.

"I told them to keep control of their emotions. This will happen in games and it's something we are training for and try to improve," said Fox. Added linebacker Brandon Marshall: "He just telling us that football's a game of emotion; it's a game of men. We get passionate and sometimes we get angry so he said [to] control that when it's with your teammates because we have games that—in the preseason—we can go and hit other people and tackle other people."The intensity was channeled from that point forward, and practice continued. But not everyone was happy with the tenor established by the brouhahas of that testy team period.

"I don't like them, to tell you the truth," said quarterback Peyton Manning. "You don't do it during a game; you do it in a game it usually costs you something important. It costs you a drive, costs you field position, gives them an easy field position. I am in to treating practice like a game, so I am not a fan of it."

The aggression is evidence of the spark that exists in the team. The lesson of Fox's mid-practice speech is about channeling it.

"He wants us to be tough, but we have to be smart when we're being tough," said linebacker Nate Irving.

"We don't want to be a dumb, tough team. We want to be a smart, tough team."

2. That intelligence is particularly crucial at linebacker, where weakside starter Danny Trevathan is sidelined for six to eight weeks because of a medial tibial impaction fracture in his left knee.

"We only have smart linebackers on this team. That's all they sign," said Marshall.

Marshall now becomes one of the most important players in the defense. He is listed as Trevathan's backup on the weak side, and replaced him following his injury Tuesday.

Marshall is two pounds lighter than the 240-pound Trevathan. They were both third-day picks in the 2012 NFL Draft, and racked up prodigious tackle totals in college.

"Danny does a great job, and I'm pretty sure they will entrust me in that same position with calling the defense, because I know I can do it," said Marshall.

3. It's one thing to see Quanterus Smith active and involved in the pass rush; that's what was expected from him, given his success as an edge rusher at Western Kentucky. But in Tuesday's work, he was ubiquitous against the run, showing the same sort of chasing speed parallel to the line of scrimmage that defines Von Miller as a run defender.

Smith's pursuit allowed him to steer runners outside. But his quickness and change of direction also permitted him to shake off blockers and engulf the ballcarrier from behind at the line of scrimmage, as he did to get to Juwan Thompson early in practice.

Smith noted in June that he wanted to add some weight to his frame; this helps him hold his ground better at the point of attack. But with his speed returning to the level that attracted the Broncos' notice prior to the 2013 NFL Draft, he has the tools to be a solid run defender when properly utilized.

4. John Boyett wasn't at the center of any skirmishes, but he continues to deliver big hits and make plays on the football. Tuesday, he lowered his shoulder into running back Jerodis Williams and delivered a ferocious shot. Big hits are Boyett's calling card, but with a deep, experienced safety corps, he'll need more than that to snag one of the 53 spots on the active roster.

5. Although item No. 3 mentioned Smith's takedown of Thompson, the day was positive for the 5-foot-11, 225-pound rookie running back. He displayed a surprising nimbleness to bounce outside to developing holes, and had one of his best blitz pickups in the red zone, standing up to safety T.J. Ward before Manning threw a pass that was intercepted by Aqib Talib. The final result was poor for the offense, but Thompson showed the awareness required of a running back in the Broncos' system.