ENGLEWOOD, Colo. -- The Denver Broncos rolled through their offseason work and into summer's training camp with a feeling that the talent at the top of their depth chart was good.

Good enough to compete with the league's heavyweights on the team's best days, good enough to rebound from a 5-11 finish in 2017 and a 6-10 finish in 2018.

But a lack of depth left them vulnerable should injuries occur, and now their house of cards has begun to topple.

Linebacker Bradley Chubb's season-ending knee injury announced Monday is the latest, and biggest, piece of injury news the 0-4 Broncos have encountered in the season's first month.

"It's a huge loss, he's one of our better players obviously," Broncos' coach Vic Fangio said of Chubb, the No. 5 pick of the 2018 draft. "He's a tempo setter, great player, great person, leader, all of that."

Chubb suffered a partial tear of his left ACL on Sunday while playing 75 of the team's 84 defensive snaps during a 26-24 loss to the Jacksonville Jaguars -- the Broncos' eighth consecutive loss dating back to Week 14 of 2018. Chubb limped off the field with little more than 14 minutes remaining in the fourth quarter, but came back into the lineup and was one of the Broncos' most impactful players down the stretch.

And now he's done for the season.

It has been that kind of year for the Broncos. The big-ticket players John Elway signed in free agency -- right tackle Ja'Wuan James (four years, $51 million), defensive back Kareem Jackson (three years, $33 million) and cornerback Bryce Callahan (three years, $21 million) -- were all among the game day inactives Sunday due to injuries.

Jackson has appeared in three of the Broncos' four games, but James suffered a knee injury 10 snaps into the season opener in Oakland and hasn't played since. Callahan has missed the preseason as well as the Broncos' first four games with a foot injury. Callahan has an issue with a screw inserted into his foot last December to aid in the healing of a fracture. He will miss another three to five weeks before the Broncos consider surgery to repair the foot or see if he can attempt to return.

Chubb's injury is the latest reminder of the shadow that the 2016 and 2017 drafts continue to cast over the Broncos' roster. Of the 16 players taken in those two draft classes, seven of them are no longer on the team -- not as starters, or quality backups or even special teamers who would all still be on their rookie contracts.

The Broncos have just one starter -- left tackle Garett Bolles -- from the '17 draft and while the Class of '16 has provided safety Justin Simmons, defensive end Adam Gotsis and center Connor McGovern as starters to go with safety Will Parks and fullback Andy Janovich, that class was topped by Paxton Lynch with the 26th overall pick. Lynch started only four games before being waived in the summer of 2018 and few things leave a mark in the NFL like a miss in the first round on a quarterback.

Those two drafts should be a big part of the Broncos' depth right now, a big part of the guts of a homegrown team that has players in a four-year window of rookie contracts. Instead there is a void.

Gutted draft classes force a team to take a more reactionary approach to free agency, placing stresses on a team's salary cap and their chemistry.

Chubb's loss will be difficult to work through because, as Fangio said, he is one of their best players, he is one of their "tempo setters," something they need on all fronts. But it is also another example of just how much this Broncos team needed so many things to go exactly as planned.