Dixon left Saturday's preseason matchup with an apparent chest injury and is questionable to return, Jonathan Jones of the Charlotte Observer reports.
In his NFL debut last week, Dixon tallied three tackles against Baltimore. The Washington product has taken reps at both cornerback and safety for Carolina in the early going, but with a lot of uncertainty surrounding Dixon and his injury, it remains to be seen if he'll be able to squeak onto the roster by preseason's end.
Johnson (Achilles) was placed on the Panthers' reserve/NFI list on Monday, Steve Reed of the Associated Press reports.
Johnson also began training camp on the active/NFI list after undergoing offseason surgery to repair an Achilles injury suffered last season with the Patriots. Although no timetable was provided for his return, Johnson could theoretically resume playing after the first six weeks of the regular season.