Cam Newton sustained a concussion after a hard hit in the fourth quarter on Sunday, and this time the Carolina Panthers didn’t take any chances.

Newton was pulled after he was hit hard, but cleanly, by Falcons linebacker Deion Jones on a successful 2-point conversion run that pulled the Panthers within 34-18. Derek Anderson came on to replace the 2015 NFL MVP. The Panthers later confirmed that their star quarterback, who did not speak with reporters after the game, had a concussion.

The Falcons, behind huge days for Matt Ryan and Julio Jones, pulled away for a 48-33 victory, dropping the Panthers to 1-3.

In the Panthers’ season-opening Super Bowl rematch against the Denver Broncos, Newton took four helmet-to-helmet shots, but never came out of the game, raising questions about whether the Panthers or officials had followed proper protocol. Defenders Brandon Marshall and Darian Stewart were later fined by the NFL.

Newton was not the only quarterback injured Sunday as Denver’s Trevor Siemian was sidelined during the Broncos’ game against the Tampa Bay Buccaneers with an injury to his left, non-throwing shoulder. The second-quarter injury led to the debut of rookie first round draft choice Paxton Lynch, who led a field goal drive and later threw a touchdown pass in a game delayed by severe weather.

Tampa Bay also sustained a significant injury in the game as four-time Pro Bowl tackle Gerald McCoy left with a calf injury during the first half. McCoy left the field early in the second quarter, walking gingerly with assistance from a trainer, and the team said he would not return.

Arizona, meanwhile, lost Carson Palmer early in the fourth quarter of their 17-13 loss to the Los Angeles Rams. Palmer was injured when his head slammed the turf on a sack by Aaron Donald. He originally was evaluated for concussion symptoms by trainers on the sideline, then taken to the locker room, not to return.

Panthers linebacker Thomas Davis also left the game Sunday with a hamstring injury early in the second half, and Carolina wide receiver Devin Funchess left the game in the fourth quarter with a toe injury.

The Washington Redskins, who lost four starters last week, had three defenders go down in the team’s victory over the Browns. Top pass rusher Ryan Kerrigan left in the second quarter with an elbow injury, fellow linebacker Su’a Cravens left in the third with a concussion and safety David Bruton left in the fourth with a concussion.

It also was a difficult day for players in the secondary.

The Ravens, who allowed four touchdown passes by Derek Carr, the last a game-winner with 2:12 remaining, lost cornerback Maurice Canady in the first quarter with a thigh injury. Safeties Eric Weddle and Lardarius Webb both underwent concussion protocol in the fourth quarter, but were cleared to return.

In the Jets’ 27-17 loss to Seattle, cornerback Darrelle Revis sustained a thigh injury in the fourth quarter and didn’t return for New York, and right guard Brian Winters left in the second quarter with a head injury after he slammed helmets with a Seahawks defender. Winters was also called for unnecessary roughness on the play.

In other injuries:

—49ers linebacker NaVorro Bowman sustained a lower left leg injury in the third quarter and left the 49ers game against Dallas. Bowman was not hit on the play, but had to be helped off the field. He was then taken to the locker room on a cart.

— Saints defensive end Paul Kruger suffered a back injury in the third quarter.

—Panthers wide receiver Devin Funchess left in the fourth quarter with a toe injury.

—Raiders tight end Lee Smith left with an ankle injury in the second quarter and linebacker Malcolm Smith left in the fourth quarter with a groin injury.

—Ravens cornerback Maurice Canady left in the first quarter with a thigh injury and tight end Maxx Williams missed most of the second half after injuring a knee.

—Patriots tight end Martellus Bennett limped off the field and defensive tackle Vincent Valentine left in the third quarter with a back injury.

—Bills cornerback Corey White was evaluated for a concussion in the fourth quarter after being shaken up while covering a punt.

—Lions running back Dwayne Washington limped off in the first quarter with a left ankle injury.