ENGLEWOOD — It was a simple passing drill.

With no defense, the quarterback dropped back. Emmanuel Sanders from the left receiver line took off and cut in sharply about 3 to 5 yards out.

His left leg gave out. It looked like he slipped, but when Sanders took his helmet off and slammed it to the ground, followed by trainers and coaches coming over to attend to him, it didn’t look good. It looked worse as he carried from the field to the locker room while hopping on his right foot and lifting his injured left leg in the air.

A few minutes later, the horrific news arrived: Sanders had suffered a torn left Achilles. Finished for the year. The Broncos then put in a waiver claim on receiver Andre Holmes, who had played for Broncos offensive coordinator Bill Musgrave when both held the same roles in Oakland in 2015-16. Holmes adds experience to a remaining Broncos receiving core that had none entering the season.

The rookie duo of Courtland Sutton and DaeSean Hamilton are the Broncos' starting receivers. Tim Patrick is the No. 3 receiver. River Cracraft will play here and there. And they'll see how quickly Holmes can mix in.

Still, none of those guys are going to make Bronco followers forget Sanders.

“You don’t really replace guys,'' said quarterback Case Keenum. "Emmanuel is obviously one of the best guys I’ve ever worked with, from what I knew about him coming in, seeing how he worked, how he handled himself and how he led. It’s surpassed all of my expectations by far and away. He’s an incredible guy. I’m not going to talk like he’s gone, I have all the trust in the world in those other guys.”

With four games remaining, Sanders was on his way to the second-best statistical season as he had 71 catches, for 868 yards and four touchdowns. He had 101 catches for 1,404 yards and nine touchdowns in 2014, his first with the Broncos.

“Seeing Emmanuel go down was a very sad situation,'' said Sutton, whose 28 catches for 558 yards now leads the club's active roster> "The guy works his (butt) off. You all see it. Everybody sees it. You hate to see that for somebody in this position. He’s having a great season. However, we’re all professionals now. We’ve got to step up—myself DaeSean, Tim, ‘Riv’ -- we’ve all got to step up and step into these roles that we’ve been handed, and not look back into it.''

The season-ending injury keeps striking the heart of the Broncos’ starting lineup. In the last 31 days, the Broncos have lost starting center Matt Paradis (fractured fibula), left guard Max Garcia (torn ACL), tight end Jeff Heuerman (fractured ribs and bruised lung) and now Sanders to season-ending injuries. And cornerback Chris Harris Jr. may well be out for the season with a fractured fibula, although there is hope he can return if the Broncos reach the postseason.

These mounting injuries, though, aren't going to help the Broncos get there. The Broncos are 6-6 with three straight wins. They play at 2-10 San Francisco this Sunday.

“I’m a product of somebody getting a chance when somebody gets injured,'' Keenum reasoned. "It could be a great start for somebody’s career, one of these young receivers who we trust. They’ve been working a long time, Court, DaeSean, Tim Patrick, all of those guys. What a great opportunity for those guys.”