Port medical report, as given to AFL.com, should see Nyhuis clear to play.
Gray was knocked out by a Ryan Nyhuis sling tackle in Sunday's nine-point loss to Fremantle at Optus Stadium.
The 30-year-old returned to Adelaide with his Power teammates on Monday afternoon.
"At this stage, he pulled up really well," Power assistant coach Brendon Lade told reporters.
"After the game, he was eating and he was fine, he didn't have a headache at all.
"He'll be assessed on Thursday or Friday."
"The positive news is Robbie is fine, he's had no ill effects so far and hopefully he'll be fine for selection.