Gresham, coming off back surgery, was on the physically unable to perform list, and Niklas, out with a hamstring injury, was on the non-football injury list.
The Cardinals signed Gresham to a one-year contract on July 24. Niklas, a second-round draft pick out of Notre Dame last year, has been plagued by injuries in his brief NFL career.
Coach Bruce Arians said both will be limited to walkthroughs for now.
Arians also said rookie outside linebacker Shaq Riddick aggravated a hamstring injury. Arians called it a grade 2 tear and said Riddick, a fifth-round draft pick out of West Virginia, will be out for ''some time.''
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