"There doesn't appear to be a bone issue so it might be something as simple as an abscess," said Nairn.
"But even if that is all, it would need to burst out in the next few days for her to be there on Saturday.
"So we will know one way or the other by about Wednesday," added Nairn, who advised officials so TAB bookmakers could suspend betting on the race.
Habibti Ivy has good gate speed and would add to the early pressure in the race, as well as putting another sizeable frame between Speeding Spur and the markers.
If she is scratched, the early leaders look to be Sunny Ruby or Prince Fearless, the former likely to cop a trail on Speeding Spur, the latter not so likely.
"As much as you never want to see any horse scratched, not having Habibti Ivy there would definitely help us," said Josh Dickie, who will drive Speeding Spur.
"Dad is thrilled with him and thinks he might still be improving so regardless of what happens he will get his chance."
If Habibti Ivy comes out Speeding Spur will become odds-on, joining two of the stars of Saturday's Ashburton trials in Dream About Me and Have Faith In Me.
They were both impressive winning, Dream About Me going close to 25 seconds for her last 400m which saw her shorten from $1.70 to $1.45 to win the opening race for 2-year-old pacing fillies.
Stablemate Have Faith In Me downed Follow The Stars in their trial and is $1.60 to bookend the programme for the Purdon-Rasmussen stable.
Meanwhile, NSW mare Valerie was a solid fifth in a 1:55.5 mile at Menangle on Saturday night as she prepares to take on King Denny in the 4-year-old trot.