I cant offer advice in reference to the original question, as both my dogs clicked with the whole 'chase' instinct straight away...
But maybe a lure would help?
A rabbit skin dummy on the lure, a few 50 yard runs letting the dog catch it, get him excited etc?
Playing with skins/ rags/ foxtails etc on pieces of string, dragging them across the floor, getting the dogs 'chase senses' going into overdrive.
I done this with my dog...always had a rag on a piece of string handy round the house....
Maybe this is the wrong advice?...maybe it would work?