Cardinals quarterback Carson Palmer left Sunday's loss to the Rams with a concussion and it will keep him out against the 49ers.

The Cardinals will not have the services of Carson Palmer in their critical "Thursday Night Football" matchup against the 49ers.

The team's starting quarterback suffered a concussion in Sunday's loss to the Rams, and while coach Bruce Arians said progress has made, Palmer hasn't passed the concussion protocol. He won't fly with the team to California and the reins will be handed over to backup quarterback Drew Stanton.

"There's no way I'm going to take any chances with him," Arians said. "He argued a little bit, but he has not cleared. He's getting much better and he feels fine. Hopefully we'll have him back next week."

Arians said he's "very optimistic" Palmer will play next Monday night against the Jets. For now, it will be Stanton under center as the Cardinals try to dig their way out of a 1-3 start. He was 4-of-11 for 37 yards with a pair of interceptions in relief of Palmers against the Rams, but did go 5-3 in eight starts in 2014 as Palmer's fill-in.

"'Next Man Up' has always been our mantra, and it's never failed us," Arians said.

The backup will be Zac Dysert, who was elevated from the practice squad this week. Arians has praised his accuracy and intelligence.

Arians said there is a package of plays Dysert can run if the need arises, although clearly the hope is for him to remain on the sidelines. While it wouldn't be an ideal scenario for the third-string quarterback to play, Dysert has been cramming in case of emergency.

"Obviously there is room to improve and room to get familiar with the playbook, but from the time I have been here I have been preparing every day, studying every day, watching film every day," Dysert said. "I feel pretty comfortable."

TAKING AWAY THE HOME RUN SHOT

It's no secret the Cardinals' deep passes have struggled to connect in 2016, especially compared to the efficiency at which they hit last season.

Offensive coordinator Harold Goodwin said opponents are keeping safeties back deep much of the time to combat the attempts.

"A lot of teams, they know our past," Goodwin said. "We like to take shots, and they're trying to eliminate them."

The Cardinals can make teams pay by running the ball against thinner defensive fronts and connecting on short and intermediate routes. That requires patience, but may be a requirement in the near future if defenses continue to force their hand.

"Any logical defensive coordinator would see we that like our chunk plays," wide receiver Larry Fitzgerald said. "When they present themselves, we still have to take them. That's just who we are. But teams are going to try to make us sustain drives, make us take six, seven, eight, nine, 10 plays to be able to put the points on the board. We can play that kind of ball too."

SIMON READY TO CONTRIBUTE

Safety Tyvon Branch was placed on injured reserve with a groin injury on Tuesday, and his loss will cause a domino effect when the Cardinals are outside of their base defense.

Tyrann Mathieu is expected to assume the role of nickel cornerback, with D.J. Swearinger taking over at safety. There could be more playing time available for Tharold Simon, the cornerback picked up off waivers from the Seahawks on Sept. 13 who has played some dime defense the past two games.

"It's just once they trust me enough to put me in more packages," Simon said. "I know they want to do more with me, but I understand I've only been here two-and-a-half, three weeks, so I understand it's about me being patient and them making sure I've got everything down."

FELLS, STINSON WON'T PLAY

Tight end Darren Fells (neck) and defensive tackle Ed Stinson (toe) won't play against the 49ers, Arians said. The absence of Stinson opens up a rotation spot on the defensive line, but Arians was noncommittal when asked if it will be filled by first-round pick Robert Nkemdiche, who has been inactive in recent games.

"His ankle looks fine," Arians said. "This is a game where if you're in the wrong gap, it's going to be a 50-yard run, so I'm not sure I'm ready to put him in there. We'll see."

Defensive tackles Frostee Rucker (knee) and Josh Mauro (chest) and cornerback Justin Bethel (foot) are listed as questionable for the game.

For the 49ers, defensive tackle DeForest Buckner (foot) and cornerback Jimmie Ward (quadriceps) have been ruled out. Defensive tackle Glenn Dorsey (knee), wideout Jeremy Kerley (ankle) and tight end Vance McDonald (hip) are questionable.