"It gave her one big bay and she settled down a bit," said Williams.
The stable is only guessing, he said, that the fact the mare was in season caused the lapse in behaviour.
"We walked her for two hours solid before the race and she was fairly quiet by the time it came to saddle her."
If Vavasour disgraced herself in the morning she more than made up for it in the afternoon, sitting outside the leader to the home bend and forging clear under her big weight.
A race earlier the Peter and Dawn Williams and Paul Richards stable won the $50,000 sprint with Natuzzi, who put up a storming finish under Chris Johnson and 60kg.
Peter Williams said the stable has not finally decided on the immediate future of Vavasour, but said the City Of Auckland Cup at Ellerslie is not on the table.
"She was nominated, but it's not the right race for her. I don't want to tax her over the middle of summer, I'd rather give her a short break now and have a crack at the Auckland Cup in March then take her to Sydney."
Speed merchant Passing Shot made a timely return to his best form at Te Rapa to confirm plans for a tilt at the north's premier sprinting prize.
The four-year-old proved too slick for his Rating 85 rivals in Saturday's Lowe Schollum & Jones Premier to boost connections' confidence ahead of the Group 1 Sistema Railway Stakes at Ellerslie on New Year's Day.
"He's a fast horse who's best on a fast track," said trainer Stephen McKee, who prepares the entire with Eddie Chippendale.
In the hands of Opie Bosson they brought an end to the unbeaten record of runner-up Snapshot.
The stable also picked up the following event with the Karaka Million hope Xiong Feng maintaining his perfect record with victory in the Wentwood Grange 2YO.
Te Rapa wrap
• Williams and Richards stable wins the $50,000 sprint with Natuzzi.
• Passing Shot proves too slick for rivals.
• Xiong Feng maintains his perfect record.
- Additional reporting NZ Racing Desk
