Master Ballarat horseman Darren Weir will prepare the impressive last-start group 1 winner in a bid to end one of racing's greatest winning streaks on Saturday.

The two horses will meet at Flemington in the group 1 Turnbull Stakes over 2000m.

“You have got to be a realist. She has won 20 in a row and you are meeting her at weight for age,” Weir said of Humidor’s task.

“I’m taking my horse to the races as a fit and well horse and if both horses run to their best and both get even luck, well you won’t beat her.

“But strange things happen in horse racing. You’ve got to be in it to win it, but realistically it’s probably nearly an impossible task. But who knows?”

Winx is a $1.18 favourite to win the race with the TAB, with Humidor rated as a $4.40 chance.

Trainer Chris Waller’s six-year-old has not raced at Flemington, where she will look to extend her winning streak to 21 races.

Winx’s last defeat came way back in April of 2015.

The horse had a comfortable three-quarter pace gallop on the steeple grass at Flemington on Thursday after producing a sharp gallop on the course proper on Monday.

Bowman said he had a “very healthy respect” for Humidor, who dazzled in a big victory in the Makybe Diva Stakes at Flemington in mid-September.

"I thought his win last start was very impressive. He beat a class field and with all due respect to Happy Clapper, I'd say he's probably the toughest opposition that she's met this preparation,” Bowman said.

"So I'm excited about that.

"Obviously there's a bit of a long tail to the depth of the field but I won't look too much into that.

"I'll just make sure that I do what I always do and give her her chance to do what she can do."

Winx is being set for the Cox Plate, where she will chase a third-straight win in that race, while Humidor is on a path towards the Caulfield Cup.

Saturday’s Turnbull Stakes is scheduled to jump at 3.15pm.