ENGLEWOOD, Colo. -- The Denver Broncos showcased the gaping holes they need to fill in the weeks and months to come during a 23-9 loss to the Los Angeles Chargers in last season's finale.

Troubles abound, but the secondary, once the foundation of one of the league's best defenses, stuck out. Chris Harris Jr. was on injured reserve, and the top three cornerbacks who played in that game -- Bradley Roby, Tramaine Brock and Jamar Taylor -- are all scheduled to be unrestricted free agents. None of the three are expected back.

As Harris has said of the secondary, "Man, I don't know what it's going to look like."

Harris wants to be back, and the Broncos would be wise to keep him given how rare his talents are -- an elite coverage player on the outside and in the slot -- but change is coming, and required, at a position nowhere to be found on the Broncos' list of worries just two seasons ago.

After trading for quarterback Joe Flacco, the secondary sits atop the list of positions to fix. The Broncos are a long way from the Harris-Aqib Talib-Roby trio that Talib once called "three dogs who lock it down."

Talib was traded last March and Roby is an unrestricted free agent coming off an inconsistent season as Talib's replacement. That leaves Harris and plenty of questions marks at cornerback. In today's chuck-it-around NFL, it's difficult to have answers on defense if you have any questions at cornerback.

Harris, who played in the Pro Bowl after fracturing his right fibula Dec. 2 against the Cincinnati Bengals, has said the Broncos' issues involve both personnel and scheme. Newly hired head coach Vic Fangio is a quality start to any defensive makeover given his Chicago Bears' defense led the league in both scoring defense and takeaways last season.

"It's like I've said, I think we just haven't evolved here," Harris said. "You know, after the Super Bowl [in 2016], it's like we kind of just got stagnant. We haven't evolved. We've got to evolve with everything ... get better as players, all of us. I just think this past year we were kind of behind."

Finding the right complement to Harris won't be easy. The cornerbacks entering free agency aren't that strong, especially beyond some 30-somethings who would be more of a stopgap measure. Personnel executives just don't let top corners get into the open market.

And the draft has been a mixed bag at the position for the Broncos in John Elway's tenure as the top football executive. Since 2013, the Broncos have used six draft picks on cornerbacks. If Roby, the first-round pick in 2014, leaves in free agency as expected, just two of those picks will be on the Broncos' roster -- Isaac Yiadom and Brendan Langley. Yiadom, who was a spot player as a rookie last season, is not yet considered to be in line as a starter, and Langley already has had trouble hanging on to his roster spot, having been shifted back and forth from the practice squad to the active roster.

The draft has some quality cornerbacks, especially near the top of the board, including LSU's Greedy Williams, Georgia's Deandre Baker, Notre Dame's Julian Love, Michigan State's Justin Layne and Washington's Byron Murphy. And Harris does give the Broncos a starting point few teams can match.

"He's a technician, and on top of that, he's hungry, he's a dog," Hall of Fame cornerback Champ Bailey said earlier this month. "Those are the types of players that you want to play with. ... They tried drafting a guy in the third round before, second round, not to name them. But they never panned out to be anything what Chris is. It's unbelievable the things he's been able to do the last eight years."

The Broncos reside in the same division as Patrick Mahomes, who just tossed 50 touchdown passes in his first year as a starter, and a still-going Philip Rivers. Mahomes had two of the five 300-yard passing games against the Broncos last season and Rivers had another -- the two combined for seven touchdown passes in those three games against the Denver defense.

Harris, linebacker Brandon Marshall and other veterans on the team's defense consistently lamented the group's inability to get the most important stops when games were still in the balance, especially on plenty of third-and-long situations that used to be gimmes for the Broncos to force a punt. Overall, the Broncos were 20th in pass defense last season.

It's difficult to escape the fact the Broncos' schedule in 2019 will feature Mahomes (twice), Rivers (twice), Andrew Luck, Deshaun Watson, Matthew Stafford, Aaron Rodgers, Kirk Cousins and Baker Mayfield.

"We've just got to get back to where we're locking people down," Harris said. "Like I've said, we just have to get up with the times with what we're doing. We just stayed the same a little bit. It's 2019 -- I have to evolve my game and we have to evolve our defense and have that dog attitude."