ENGLEWOOD, Colo. -- Denver Broncos coach Vance Joseph has watched his team overcome obstacles this season, using words like "grit" and "fight" to describe his players' efforts.

Now they'll need those two things more than ever, as wide receiver Emmanuel Sanders was lost for the season Wednesday with what team officials believe is a torn left Achilles tendon. Sanders suffered the injury in Wednesday's practice, or roughly 72 hours after cornerback Chris Harris Jr., a three-time Pro Bowl selection, fractured a fibula against the Cincinnati Bengals.

That's one of their premier players on offense and one of their premier players on defense out with injuries just as the team had finally clawed its way back into the playoff race.

"This is the 2018 Denver Broncos," said quarterback Case Keenum. "Nothing's been handed to us -- we're going to earn everything we get."

It also means a team that has leaned, and leaned hard, on its rookie class will do so again. Because while necessity may be the mother of invention, desperation might be the dad. In Sanders' case, he was already in a wide receivers meeting room each day with four other players who either were rookies or had spent much of their rookie years in 2017 on the Broncos' practice squad.

That was the choice the Broncos had largely already made when they shipped Demaryius Thomas to the Houston Texans on Oct. 30. At the time it put Sanders on the depth chart with two rookies (Courtland Sutton and DaeSean Hamilton) and two inexperienced players (Tim Patrick and River Cracraft).

The Broncos claimed Andre Holmes, a 30-year-old in his seventh season, off waivers less than an hour after they had finished Wednesday's practice. The Broncos saw Holmes plenty during his four seasons with the Oakland Raiders, and Holmes had a touchdown catch against the Broncos last season when he was with the Buffalo Bills.

But Holmes or no Holmes, it will be the youth movement at wide receiver that determines how the Broncos move the ball in the passing game in the weeks to come.

"When you see somebody go down, it sucks, but each person who has been hurt will tell you that the person replacing them has to go in and do their job," Sutton said. "If they don't, the team ultimately suffers and nobody wants to see the team suffer."

What that means for the Broncos is Sutton has to be, and play like, a No. 1 receiver. He's won some matchups this season as a complementary player, often physically overwhelming defensive backs, but now he's going to get a steady diet of top coverage players who would have been covering somebody else if the Broncos were anything resembling a healthy team.

Hamilton, who hasn't had more than three targets in any game this season, is also now essentially thrust into a starting role.

"What week is it? Fourteen? So he's no longer a rookie," Joseph said. "He has to go play. Along with Tim Patrick. Along with River Cracraft."

On defense, the Broncos will spend this week trying to figure out what they'll do without Harris, who is usually the starting point for what they will do in coverage each week.

They signed a veteran there, too, in Jamar Taylor, a former second-round pick by the Miami Dolphins, but the Broncos will need to lean on rookie cornerback Isaac Yiadom. Yiadom, even with the expected first-year mistakes, has shown he's willing to line up and play with confidence even after things have gone sour in a game.

"And you have to do that at corner," Harris said last week. "You can't hide. I've said, if you're scared, go to church. He comes right back and lines up -- that's what it takes."

The Broncos have never needed this much from a rookie class in John Elway's tenure as the team's chief football decision-maker. Sure, they've needed rookies to step forward before and gotten what they've hoped, and they've been surprised by a rookie or two stepping forward.

But these Broncos hope and need a lot more than that. They have slugged it out with the league's best this season, taken more than their share of football lumps on the way to 3-6 and yet still they scrapped their way back to 6-6 and the back edge of the AFC playoff race.

They've believed all along this season they could be better than what people outside their building predicted. And now they need some of their youngest players to help make that true.