The NFL acknowledges that one of the game officials should have noticed that 18 seconds were incorrectly run off the clock late in the fourth quarter of Pittsburgh's 24-20 victory at San Diego.
League spokesman Michael Signora says in a statement emailed Monday that "an error by the clock operator" after a touchback allowed extra time to run off, and "it is the responsibility of the side judge to supervise the timing of the game."
The statement adds: "Had the side judge or any of the other six on-field officials noticed the timing error, they could have corrected it."
The NFL will review the work done by the clock operator and game officials.
Panthers: LB Luke Kuechly returns
CHARLOTTE, N.C. — Panthers middle linebacker Luke Kuechly returned to practice for the first time since suffering a concussion in the Carolina's season-opening win against the Jacksonville Jaguars.
The four-year pro spent four weeks in the NFL's concussion protocol and missed three games before being cleared to return. The Panthers had a bye last week and travel to play Seattle on Sunday.
Kuechly, wearing pads and a helmet, was first in line during individual drills on Tuesday, hitting the blocking sleds seemingly as hard as he could.
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Wide receiver Jerricho Cotchery also practiced after missing the last two games with a high ankle sprain.
Defensive end Jared Allen did not practice after pinching a nerve in his back in the team's Week 4 win against Tampa Bay.
Ravens: Jason Babin among cuts
OWINGS MILLS, Md. — The Baltimore Ravens have added three cornerbacks to their porous, injury-riddled defense.
On Tuesday, Baltimore signed free agent cornerback Shareece Wright, who played 14 games with San Diego last season. He was on the San Francisco 49ers' roster this season, but did not play.
The Ravens also signed Asa Jackson and Charles James off their practice squad.
To make room for the newcomers, Baltimore put cornerback Will Davis on injured reserve and cut cornerback Rashaan Melvin and linebacker Jason Babin.
The moves come after Cleveland's Josh McCown passed for 457 yards Sunday in a 33-30 overtime defeat.
Baltimore is 1-4, the worst start in franchise history. The Ravens face the 49ers on Sunday.
Bills: New team for QB Josh Johnson
ORCHARD PARK, N.Y. — The Buffalo Bills have signed free-agent quarterback Josh Johnson in a move that raises questions regarding the status of banged-up starter Tyrod Taylor.
Johnson was signed Tuesday, a day after coach Rex Ryan said Taylor was "beat up" following a 14-13 win against Tennessee. Ryan didn't go into specifics, but noted the quarterback will be monitored through the week as Buffalo (3-2) prepares to host Cincinnati (5-0) on Sunday.
Taylor missed one play against Tennessee after turning his left ankle while being tackled after a 24-yard run. Taylor's backup is former starter EJ Manuel.
Johnson was signed a day after being released by Indianapolis. In seven seasons, he has 1,042 yards passing, five touchdowns and 10 interceptions in 29 games, including five starts.
The Bills also cut kicker Billy Cundiff.
Jaguars: QB signed with Bortles hurt
JACKSONVILLE, Fla. — The Jacksonville Jaguars have signed Jeff Tuel to the practice squad, giving them a third quarterback in case Blake Bortles can't play this week because of a sprained throwing shoulder.
Bortles injured his right shoulder early in a 38-31 loss to Tampa Bay on Sunday. He finished the game, completing 23 of 33 passes for 303 yards and a career-high four touchdowns.
Bortles is not expected to practice Wednesday, leaving backup Chad Henne to get first-team repetitions while Tuel runs the scout team.
The Jaguars claimed Tuel off waivers from Buffalo in June. He spent training camp and the preseason with Jacksonville before he was waived in August. Tuel, who started a regular-season game for the Bills in 2013, played in one preseason game this year. He completed 6 of 11 passes for 63 yards against the New York Giants.