According to Adam Schefter. "Only players with a 'major injury' who are placed on Reserve/Injured after 4:00pm, New York time, on Tuesday, September 4, or thereafter, will be eligible to be reactivated at a later time."
Hartline would be the prime candidate depending on how long it looks until he's ready. Outside shot it's Garrard, which would immediately ignite the Matt Moore trade rumors.
I don't think Garrard makes the list. I think he gets cut. If he's on roster Week 1, he is guaranteed his entire salary. I don't think the Dolphins want to do that. But at the same time they can't cut him until he's unhealthy otherwise they'd have to give him an injury settlement. That creates an interesting dynamic over the next week and a half.
Only reason to keep Garrard on there is IF Moore is traded away. Right now Garrard can't even run on his knee. Can't keep both him and Moore, so right now Garrard is odd man out.