The Broncos lost veteran cornerback Champ Bailey and linebacker Wesley Woodyard from their defense in free agency, leaving them without two of their captains from the 2013 campaign going into next season.
Harris told the club's official website: "I feel like last year, I definitely took a step up in the leadership role and was involved with a lot of the film work and gameplanning and stuff like that.
"I definitely feel like I could take another step in doing that and being a little bit more vocal in the locker room and making sure everyone is ready.
"Going into my fourth year here, learning under Champ, he kind of passed me the baton. I'm just excited to be able to step up into that role."
The 25-year-old missed his side's defeat in the Super Bowl against the Seattle Seahawks with a torn ACL.