Glen Boss will be in the spotlight with Melbourne Cup favourite Puissance De Lune in the Group One Underwood Stakes and also has strong chances on Saturday's undercard at Caulfield.

But one of the horses Boss was most looking forward to riding has been ruled out with three-year-old filly The Huntress scratched late on Friday from the Group Two Thousand Guineas Prelude.

Boss's other rides in the lead-up to the Underwood, which is the final event, include stayer Mr O'Ceirin who is out to go one better in the Naturalism Stakes after finishing runner-up to Folding Gear last year.

The winner of the Naturalism (2000m) is exempt from ballot for the Caulfield Cup.

"He's probably one of my best rides for the day," Boss said of Mr O'Ceirin.

The Ciaron Maher-trained stayer has an outside barrier to contend with but Boss isn't concerned because the on-pacer isn't that quick in his first 100m.

"If you draw inside you actually have to ride him to hold your spot but from out there all you have to do is sit on him and he just rolls forward. And he's happier that way," Boss said.

The champion jockey also links up with the Mike Moroney-trained Rhythm To Spare in a 1400m handicap having partnered the four-year-old in his past four starts.

Rhythm To Spare scored a first-up win at Sandown last month after campaigning in Queensland during the winter where he ran second to Hawkspur in the Grand Prix Stakes (2200m) and fourth to the same horse in the Queensland Derby (2400m).

"He's a proper horse and he's got that good form from the winter," Boss said.

"And he's more of a sprinter-miler than a stayer."

Puissance De Lune is one of the headline horses in Saturday's star-studded Underwood Stakes and while Boss expects him to run well, he doubts he can beat favourite Atlantic Jewel over the 1800m at this stage of his preparation.

What Boss is confident of is that he's learned from the Makybe Diva Stakes where he said he exposed Puissance De Lune too early which left him a "sitting shot" for Foreteller who grabbed him on the line.

"I'm a hard task master on myself and I looked at that as a pretty ordinary ride, and I don't make mistakes twice," Boss said.

"Never have. Never will."