Sunday marked a rough day for NFL quarterbacks with Kirk Cousins, Matthew Stafford and Kenny Pickett all suffering injuries.
Cousins' injury appears to be the most severe with Minnesota Vikings coach Kevin O'Connell saying the team fears he sustained an injury to his Achilles tendon.
The four-time Pro Bowl QB has never missed a game due to injury in his 12-year career but is in danger of being lost for the remainder of the season if the tendon is indeed torn, which has been reported by NFL Network Insider Ian Rapoport.
He is scheduled for an MRI on Monday.
Cousins left in the fourth quarter of the Vikings' 24-10 win over the Green Bay Packers after being sacked by Kenny Clark - the second consecutive play he was sacked.
"We are fearing an Achilles injury," O'Connell said. "The severity of that, I do not know at this point, but I do know that's what our fear is at the moment."
Cousins threw for 274 yards and two touchdowns in leading the Vikings to a third straight win to even their record at 4-4. The 35-year-old is playing some of the best football of his career, throwing for 2,331 yards with 18 touchdowns to five interceptions while posting a 103.8 rating.
His backup, rookie Jaren Hall, made his NFL debut upon replacing Cousins and completed three of four passes for 23 yards.
O'Connell wouldn't commit to starting Hall next Sunday against the Atlanta Falcons, so the Vikings could look to signing a veteran free agent to take over the offence.
Stafford injured his right thumb in the Los Angeles Rams' 43-20 blowout loss to the Dallas Cowboys.
The 35-year-old initially hurt the thumb on his throwing hand on a failed 2-point conversion pass in the final seconds of the first half and then exited for good after aggravating the injury after catching a 2-point try on the Rams' first possession of the third quarter.
Brett Rypien entered at quarterback the next time the Rams got the ball and completed five of 10 passes for 42 yards in his first action of the season. Stafford finished 13 of 22 for 162 yards with a touchdown and interception.
Coach Sean McVay said he didn't have an update on Stafford's injury after the loss, which dropped Los Angeles' record to 3-5.
Pickett left the Pittsburgh Steelers' 20-10 defeat to the Jacksonville Jaguars with a rib injury.
Pickett was injured on a hit by defensive end Adam Gotsis after throwing a pass that fell incomplete in the final minute of the first half.
After the game, coach Mike Tomlin said he didn't know the severity of the injury to Pickett, who was 10 of 16 for 73 yards before exiting.
The Steelers have a quick turnaround, with their next game Thursday against the visiting Tennessee Titans.
If Pickett can't play, Mitch Trubisky would make his 56th career start - and first of the season.
Trubisky, who played in the second half of Pittsburgh's 30-6 loss to Houston in Week 4 after Pickett left with a bone bruise in his knee, went 15 of 27 for 138 yards with a touchdown and two interceptions against the Jaguars.