A last-to-first debut win from two-year-old Top Sight at Caulfield could have earned the filly a shot at one of the Blue Diamond lead-ups.

The Ciaron Maher-trained Top Sight stepped out in Wednesday's Jacob Park Thoroughbreds Plate (1000m) and trailed the field to the home turn before sprinting down the outside to win by 1-1/4-lengths.

Top Sight ($11) defeated Sakitto ($5) with favourite Cautious ($2.70) another three-quarters of a length away third.

The race changed complexion less than 20 minutes before start time when Fontein Ruby, which was favourite, was scratched on veterinarians advice after rearing in the raceday stalls and hitting her head.

Maher said the Blue Diamond Preview or Prelude for fillies could be an option for Top Sight to be tested in better company.

"We'll just see how she pulls up, but she's a no frills sort of filly and is quite good mentally," Maher said.

"She hasn't been shin sore or anything."

The filly isn't nominated for next month's Group One Blue Diamond.

Top Sight went into her debut without an official trial but Maher said the youngster had performed pretty well in a couple of jumpouts.

"They ran along today and she was beaten for speed and then finished off strongly," Maher said.

Jockey Michelle Payne believes there is plenty of upside to the filly but had expected Top Sight to race near the speed, having led in her two jumpouts.

"The horse on my outside just gave her a little squeeze early and it just put her out the back," Payne said.

"The speed was genuine and she was just a bit lost being the first time she had been back in behind them."

Payne said she was still happy where she was because the speed was genuine and was impressed by the way the filly let down in the straight.

"She rounded them up and won easily in the end," Payne said.