The star tight end was listed as questionable on Friday due to a torn plantar fascia in his right foot that caused him to miss the last two games.
Gates didn't practice on Friday. He did limited work on Thursday, his first practice since Oct. 29, but was in extreme discomfort following a workout designed to see if he could tolerate the pain associated with live action.
"It didn't get any worse," coach Norv Turner said. "He went through the walk-through. It doesn't help him to go two days in a row, so we'll just see where he's at on Sunday."
The Chargers are taking the same approach with wide receiver Malcom Floyd, who was a limited participant in Friday's practice after missing the previous two with a sore hamstring.
"For what he did on a limited basis, Malcom was all right," Turner said. "We're treating him like Gates in that we'll see where he's at on Sunday."
The Chargers' injury report was a long one. Running back Ryan Mathews was listed as doubtful with a high ankle sprain and will not play. Right guard Louis Vasquez (stinger), defensive back Donald Strickland (hip), tight end Kris Wilson (back), defensive lineman Travis Johnson (shoulder) and strong safety Steve Gregory (shoulder) were listed as questionable. Fullback Jacob Hester (foot), tight end Randy McMichael (hamstring) and receiver Legedu Naanee (hamstring) were listed as probable.