Te Akau training partner Jamie Richards says the final choice of who their retained rider would partner was entirely Bosson's.
"We didn't steer Opie one way or the other but the filly had been working very well before that last start win," he said.
"And like everybody else, we get a boost in confidence about her chances because of Opie's choice because he knows our other horses very well too. So maybe she is our top chance pre-draw but I think Al Hasa will be fitter for what he did last start at Ellerslie and we are thrilled to get Hugh on him."
Richards admits Sword Of Osman, who has only had one start but was stunning on debut at Awapuni, looks more a natural three-year-old than the jump and run juvenile types who often win races like the Million but says the gelding has "that x-factor that we will be all interested to see".
Less favoured fillies Pinot Grey and The Real Beel round out the Te Akau assault on the race but their connections shouldn't be too put off by their outsider status - Melody Belle paid $32.40 when she beat equal favourite Hasahalo last season.
Hasahalo returns in the three-year-old Million on Saturday night, meaning a clash of the 1000 Guineas and 2000 Guineas (Embellish) winners.
Embellish got too far back and had to come wide on the wrong part of the track at Ellerslie on Boxing Day but hasn't raced since, instead pleasing the camp with his work between races last week.
Hasahalo's trainer Stephen McKee will be joining Ellerslie bosses hoping for a fine build-up to the twilight meeting as his filly loathes wet tracks.
She is rated a $10 chance, with Embellish at $3.20 pre draw while market drifter Ever Loyal was among those to take advantage of the chance to gallop on Ellerslie's course proper yesterday morning.
Beaten when he never looked happy as a hot favourite at Ellerslie 10 days ago, Ever Loyal thrilled trainer Tony Pike with his work yesterday with Leith Innes in the saddle, as he will be on Saturday.
"I couldn't be happier with him and we will be looking to ride him handy and if they aren't going any clip we will be happy enough to roll to the lead with him," says Pike.
Pike will also have promising sprinter Merlini in the $70,000 Mongolian Khan Trophy where he takes on flying fillies Melody Belle and Gift Of Power. "Leith was really pleased how he handled his first look at Ellerslie this morning too and while the fillies have an experience edge on him it is a good race to target."
Karaka Million night
Where: Ellerslie
When: First race 4.41pm, Saturday
What: $1 million Karaka Million; $1m Karaka Million Classic (three-year-old); $200,000 Windsor Park Stud City Of Auckland Cup; $100,000 Westbury Classic; $70,000 Brighthill Farm Concorde; $70,000 Mongolian Khan Trophy