Brown (heel) was listed as a non-participant on Thursday's injury report, Darren Urban of the Cardinals' official site reports.
Brown's heel issue only emerged Wednesday, when the Cardinals considered him limited. Now that he didn't log any activity one day later, there's a chance he suffered the injury at Wednesday's session, but there's also a chance that Thursday's DNP is a precautionary measure. Ultimately, Arizona may provide some clarity into the situation when it posts its final practice report of the week Friday.