The Panthers placed Christensen (hamstring) on injured reserve Tuesday, Darin Gantt of the team's official site reports.
Christensen will be required to miss the first four games of the regular season on IR before becoming eligible to return to the Panthers' active roster, though it's possible he works out an injury settlement with the team between now and Week 5. Mike Kaye of ESPN.com reports that general manager Dan Morgan said he expects Christensen to return at some point during the regular season, but it remains unclear when that will be.