Palmer sustained a knee injury against the Kansas City Chiefs in Week 7 but played against the Chicago Bears in Week 8 after just one day of limited practice. Against the Bears, Palmer aggravated the injury in the first quarter while running a route. He crumpled on the field and punched the ground as trainers helped him but eventually returned and finished the game.
He walked with a significant limp after the win and did not practice this week.
In an Instagram post Tuesday, which included a photo of Palmer punching the Sofi Stadium field in frustration after the injury, he wrote: "I could never quit on my guys. I must've missed the part that said stop if it hurts."
The post appeared to indicate that he could play through the injury, but Palmer will miss at least the next four weeks.
"I think it's a big opportunity for the whole group," coach Brandon Staley said. "When I look at the guys that we're going to have step up, it's not going to just be the receiver position. It's going to have to be the tight ends and the backs too."
The Chargers activated wide receiver Jalen Guyton and defensive lineman Otito Ogbonnia from the physically unable to perform list. Guyton, one of the fastest players on the team -- boasting a 4.39 40-yard dash -- tore an ACL in Week 3 last season. His return will give the Chargers a quick receiver who could help keep their injury-ravaged receiver room afloat.
Los Angeles had relied on Palmer after wide receiver Mike Williams tore the ACL in his left knee in Week 3 against the Minnesota Vikings. Palmer had 15 receptions for 294 yards since Week 3, including five catches for 133 yards against the Chiefs in Week 7.
With Palmer and Williams out, the Chargers will rely on rookie first-round pick Quentin Johnston, who hasn't had a significant impact yet this season. Johnston had career highs in receptions (five) and yards (50) last week.
"I think Quentin, every time he goes out there, he's improving," Staley said. "As long as he can continue that progress, then good things are going to happen. We feel confident in that group."