There were many shocked by the $91 debut win of Open House, except for those close to filly, especially trainer Kathryn Durden.

The three-year-old scored at Cranbourne last month but won't be anything like those odds when she lines up in the Argyle Maintenance Handicap over 1000m at Sandown on Wednesday.

Open House was a betting ring drifter from $41 but Durden was quietly confident she would run a nice race.

She has been asked many times since whether the win was a shock.

"What I said to the owners was on her trials and her work she should be in the finish," Durden said.

"She had done everything right so the $91, that was the surprise."

Durden has taken Open House along quietly since the filly arrived at her stable as a yearling.

She said she was asked to take her on to give her the necessary time to develop as the filly was not quite correct in her forelegs.

The plan worked as Open House recorded a comfortable debut win and has shown no signs of any leg problems.

Durden would liked to have drawn better than the outside barrier in the seven horse field, but said being away from the fence was an advantage at last Saturday's Sandown meeting.

Jarrod Fry, who rode the filly in her debut, keeps the ride on Wednesday with the remaining six runners all to be ridden by claiming apprentices.

"Because she can be a bit temperamental I elected not to claim off her," Durden said.

"Jarrod has ridden her in all of her trials and he knows her well so I just thought at this early stage it's best to keep him on her.

"I know everyone else has claimed but it's a 1000 metre race, not a 3000 metre race."

Wednesday's race is a step up in grade but Durden goes to Sandown with the knowledge the runner-up at Cranbourne, Go Public, has since gone on to win an 1100m-maiden at Echuca.

"It's a step up in class but I'm happy with her and she's done everything right since her win," Durden said.