Ertz (calf) wasn't spotted on the field during the open portion of Thursday's practice, Tyler Drake of ArizonaSports.com reports.
Unless Ertz fits in some work in behind the scenes, he'll be listed as a non-participant on the Cardinals' injury report, which marks a step back from his limited activity a day earlier. It's possible Ertz's potential absence is a pre-planned maintenance day, but it nonetheless creates further questions about his availability for Sunday's season opener against the Chiefs. Head coach Kliff Kingsbury previously listed Ertz as "day-to-day" earlier in the week, though that description doesn't shed much light on the tight end's status for the opener.