While New Zealand's best rider is confident he will be on Imperatriz and says the stable intend to start her even on what could be a very heavy track, he is only guessing whether she can show her best.
"When it gets as heavy as it is going to be you really don't know if these top horses will handle it," said Bosson.
"You would think she is too brilliant to be a natural heavy track horse so I don't think she will be at her best but I suppose the question is whether she can get away with it.
"And that is really impossible to tell," he added.
"It might come down to just how heavy and challenging it gets."
On a good or even soft track Imperatriz could slide well into red-odds territory and while nobody would be surprised to see her storm down the middle of the track to win, her $1.90 quote is hardly any real spoil.
The Allan Sharrock-trained trio of Butler, Tavi Mac and Darci La Bella will all handle the wet so any of them could win, while those looking for value could opt for a place or top four bet on Gino Severini.
Gino Severini's first-up record is outstanding, including running second in this race last year, and he has never had a bad race fresh-up since coming to New Zealand.
He touched $5 to run in the top four yesterday and he at least has an element of been-there, done-that about him in a race of question marks.
The Te Rapa meeting is a beauty, with some deep races highlighted by the Rating 75 over 1400m (race five) which could be a serious spring form pointer.
There will also be plenty of Kiwi interest across the Tasman with Dragon Leap contesting the A$1 million Memsie Stakes at Caulfield, where the track could also be heavy, but not as testing as the two meetings here at Te Rapa and Awapuni.
Dragon Leap looked a superstar as a three-year-old but has raced only five times since starting favourite in the New Zealand Derby 2 years ago, being bugged by persistent niggles.
He is rated a 40-1 chance in a Memsie loaded with serious Group 1 horses, his task reiterating the mountain New Zealand's elite gallopers have to climb when they cross the Tasman for Australian Group 1s this spring.