No, Kerby Joseph is not expected to play in Week 1. He was officially placed on the PUP list on August 30 as the Lions finalized their 53-man roster, which means he'll miss at least the first four games of the season (from the Kerby Joseph page).
He has a chronic cartilage condition in his left knee — his last game appearance was October 12, 2025. Dan Campbell set expectations clearly, saying "if we got him back for the first game, that would be a bonus," which signaled the team wasn't counting on him. He'll be eligible to return as early as Week 5 (Oct. 11), assuming he gets cleared to practice after two weeks on reserve/PUP under the NFL's new rule.
Veteran Chuck Clark is expected to start in his place alongside Brian Branch (who's also out with an Achilles injury, so Detroit's safety depth is thin).