The latter had nothing to do with Bosson's ride, Melody Belle simply underperformed at Te Rapa, and that is why she has lost favouritism for the 2000m weight-for-age, rated $2.80 to Avantage's $2 opening quote.
The market suggests Bosson has ended up on the right horse, but he isn't sure.
"It isn't up to me and I wish Troy all the best on her because she has been such a great mare to all of us," says Bosson.
"But I really don't know which one I favour more. Melody Belle has been such a great horse for such a long time but Avantage is really stepping up.
"I have been really happy with how she is racing and in her work this week and I think I might be able to ride her a little more relaxed from that draw over 2000m," says Bosson of Avantage.
"But I saw Melody Belle fly past in trackwork on Tuesday and she looks great. So it is going to be an interesting race."
With six Group 1 winners in the field it would be arrogant to think the two Te Akau mares have it to themselves but they have won the last two runnings of this race and have completely dominated the Group 1 races they have contested in this country for the last two years.
Whether Avantage deserves to be clearly the favourite over Melody Belle may come down to tempo as the race doesn't look likely to be brutal and if it becomes a 2:2-2:4 type 2000m (on a decent track) then Avantage — settling handier from barrier three — might have a tactical advantage.
Still, the last two times the great mares have met at weight-for-age, at Hastings in the spring, Melody Belle was dominant, more so over the longer trip.
Add in Concert Hall and shock Herbie Dyke winner Royal Performer and the Bonecrusher becomes what it should be, a fitting grand final to the Group 1 weight-for-age 2000m season.
Although Bosson isn't certain he is on the right Jamie Richards-trained runner in the Bonecrusher, he feels more confident aboard Sword Of State in the $200,000 Sistema, even up against Karaka Million winner On The Bubbles.
Sword Of State thrashed On The Bubbles when the latter was returning from a short break at Matamata two weeks ago and is drawn to lead and control the race.
"I think he has improved since Matamata and he felt very sharp this week.
"I know On The Bubbles is a very good horse but I think I am on the right one and he will be hard to beat, especially if he can lead like he did last start."
Bosson's other Group 1 ride is In A Twinkling in the Auckland Cup, a race he has the ability to win but there have to be doubts over his stamina if it becomes a hard-run 3200m.