Todd Davis doesn’t quite know how he got the name or why he’s sporting it now, but it stuck and he’s keeping it. Davis is known as “Thunder,” a nickname bestowed upon him by fellow Broncos linebacker Brandon Marshall, who labeled himself “Lightning.”

“I think I just like the heat and playing in the run game,” said Davis, wearing a wide grin. “I think that’s how I got it.”

This season, Davis has taken over Marshall’s spot as Denver’s middle linebacker, as Marshall moved over to the weakside position left vacant by the departure of Danny Trevathan. While Davis and Marshall had joined forces in stints over the past two seasons, with Davis filling in with injuries, this year is their first as true starters together. Related Articles September 22, 2016 Broncos’ Von Miller credits “Dancing with the Stars” with improving his football consistency

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It’s the beginning to what Davis hopes will be a long stay as an NFL starter. But the truest beginning was Dec. 22, 2014, on “Monday Night Football” against the Bengals in Cincinnati, where Davis made his first start at the position and had his coming-out party as a potential piece of the Broncos’ future.

Sunday, Davis will be back in the city where it all began, this time with a larger role and larger expectations, relying on his preparation and his past to validate his rise from undrafted free agent to starter.

“I have to show 31 other teams who didn’t see something in me that I have it,” Davis said. “I definitely feel like there’s a chip on my shoulder. Being undrafted really did help me. It pushed me to elevate my game to the next level. I feel like I have to prove everybody wrong.”

“You see the flashing lights and you can forget what brought you here. If you don’t play well on the field, those lights will dim real quick.”

— Todd Davis

Marshall expected a rebuilding of sorts when Trevathan, his partner in crime inside, departed for Chicago in March. In two seasons starting together, the duo had a silent but strong connection, rarely needing communication on the field or the sideline to understand what the other was thinking.

“Sometimes (Todd and I) have a play in practice or a play in the game and we’ll go to the sideline and discuss it, whereas sometimes with me and Danny we wouldn’t have to because it would almost be automatic, like, ‘Bam, OK, we got it,’ ” Marshall said. “Me and Todd will get there. Sometimes we see things differently, whereas, if we’re comparing the two, me and Danny usually saw things a lot of the same.”

The Davis File A snapshot look at Broncos middle linebacker Todd Davis: Third-year linebacker who was claimed off waivers from New Orleans in November 2014.

In three seasons has 43 tackles (29 solo), 0.5 sacks, two pass breakups, one fumble recovery and 12 special-teams stops.

Made first start on “Monday Night Football” in Cincinnati on Dec. 22, 2014.

Named Broncos’ defensive player of game in Week 1 victory vs. Carolina.

Ranks second on Broncos with 12 tackles this season.

The foundation had been laid with Davis. But to ease his transition from primarily a special-teams player to starter, he took to film study. Hours and hours of it.

Davis said he watched more film than he ever had before to meticulously pick apart plays and technique, and to watch Trevathan and Marshall at work to hone his skill and decision-making. Davis also lost weight to improve his quickness and endurance, and he heeded the advice of Marshall.

“He just mostly tells me what he sees and things that he looks for,” Davis said. “Keys and tendencies that he’s learned over the years of playing and starting that you don’t learn unless you’re in the moment. So when the moment arrives, I’m like one step ahead. It helps me out a lot.”

The biggest changes in Davis were apparent during organized team activities this past offseason. Marshall said the “quiet and stiff” guy faded.

But Davis’ smarts never did.

“I saw a new Todd Davis,” Marshall said. “He knew it was his time, because Danny went to the Bears. He knew he had a shot, so I think he really came out of his shell.”

Davis was informed that the starting job was a competition between him and Corey Nelson.

“Todd just exploded on the scene in practice, and you couldn’t deny the guy,” Marshall said.

But for Davis, the drive started long before he arrived in Denver, and long before Trevathan bolted for Chicago.

Within five months of signing with the New Orleans Saints as a college free agent in 2014, Davis was waived four times before latching on with the Broncos. The opportunity to prove his potential might have first arrived in Cincinnati in 2014. But the opportunity to prove his staying power arrived last month, when he was appointed the Broncos’ new starter inside.

In the season opener against the Carolina Panthers, Davis emerged as Denver’s leading defender, making a team-high seven tackles (six solo), plus half a sack. The effort earned him the team’s defensive player of the game award and high praise from coach Gary Kubiak. Entering Sunday’s game against the Bengals, Davis ranks second on the Broncos in total tackles (12) behind safety T.J. Ward (13).

“I really think that when you’re a player and you’re a backup … you’re a special-teams player, you’re a good role player and then all of a sudden you get a chance because somebody leaves. It’s amazing to watch guys say, ‘I’m not going to let this go,’ ” Kubiak said. “And that’s what you see from Todd, and through the whole offseason it was extremely important to him to prove to the defense, ‘Hey, I can pick up the slack, hey I can do this.’ He’s done it.”

“Thunder” has come a long way.