ENGLEWOOD, Colo. --Defensive ends Zach Kerr (knee bruise) and Jared Crick (back spasms) were ruled out for Monday night's regular-season opener against the Los Angeles Chargers, Head Coach Vance Joseph announced after practice Saturday morning.

Kerr and Crick will be joined on the sideline by running back Devontae Booker (fractured wrist) and Paxton Lynch (sprained right shoulder).

Crick, who was injured during practice Aug. 14, practiced Monday, Wednesday and Thursday before sitting out the last two days. Kerr, who suffered his injury against the Green Bay Packers on Aug. 26, has not practiced since then.

"I think Jared is getting better, but he's not well enough to play a football game right now," Joseph said. "And in our opinion, if we put him out there this week -- which we could probably -- it would hurt us moving down the road. As a group discussion, we thought resting him this week would help us down the road with Jared Crick."

Nose tackle Kyle Peko is listed as questionable, but he practiced throughout the last two weeks after being moved off the physically-unable-to-perform list because of a foot injury he suffered during OTAs.

"Kyle Peko has gotten better fast," Joseph said. "He practiced the last two days and looked OK."

With two defensive linemen out and Peko questionable, Joseph said that he was not yet sure whether he would make a roster move to bolster the defensive line before Monday's game.

"Every option is going to be explored," Joseph said.

With Kerr and Crick out, Adam Gotsis and Shelby Harris are likely to see extensive playing time. Gotsis started the preseason games against the 49ers and Packers because of injuries to Crick and Derek Wolfe, and Harris worked with the first team against Green Bay after Kerr was injured, setting him up for a three-sack performance that helped secure his place on the 53-man roster.

"When you watch the San Fran[cisco] game, when you watch the Green Bay game, those guys played well," Joseph said. "So that's what I expect on Monday night. That's why they're here. Gotsis is a second-round pick; he's a guy with a bright future, and Shelby Harris had a hell of a camp.

"What they did in preseason, I expect them to do on Monday night. That's why they're here."

Harris' preseason play caught the eye of Wolfe.

"I'm really impressed with Shelby," Wolfe said. "I thought Shelby had all the tangibles to be a good player, anyways -- just his build and his quickness and his strength, he's a strong guy. He comes out every day, and he's working. He wasn't used to [Defensive Line Coach] Bill Kollar's up-tempo individual drills and stuff like that, but once he got used to it, he's just done nothing but getting better, so I'm happy with that."

OTHER NOTES:

... Joseph added that Booker is "on schedule" in his recovery, but said that he did not have an exact timetable as to his return. Booker has not practiced since OTAs because of his injury.

... Running back Jamaal Charles had another full practice Saturday after getting Thursday off to rest and is "ready to go," Joseph said.