Since Palmer mastered Arians' system halfway through the 2013 season, he has been one of the NFL's most effective quarterbacks, sporting a 27:12 TD-to-INT ratio and a 96.1 passer rating.
Although Palmer's speedy return to practice defied conservative expectations, Campbell said that the quarterback "looked good" in recent practices.
"He's proved to them that he's 100 percent," Campbell said. "... He's out there making every throw."
If Palmer stays healthy for 16 games, the NFC West could boast two of the three best teams in the conference this season in Arizona and Seattle.