Will Clarken is unsure how his six-year-old mare Bella Vella will come back after her best-ever preparation but he believes the signs are extremely positive.

The Adelaide mare will start in the Group Two McEwen Stakes over 1000 metres at Moonee Valley on Saturday.

"She's feeling really happy with herself. She's walking around with an air of authority about her after having had an undefeated preparation," Clarken said.

"I can't fault her but when they're coming off a peak run, as she did when she won the Sangster, you want to see them do it again.

"I'm really happy with her. She cruised in with her trial at Morphettville last week and she's developed into a lovely looking older mare. She's really furnished.

"I'm looking for her to run well so we can go into the Moir Stakes at her next start."

Clarken admitted barrier eight in a race with several fast horses was an awkward draw.

"I'll leave it to (jockey) Jamie Kah. I'd love her to be able to cross but Jamie knows the horse and she's a rhythm-and-tempo rider so I'll leave it to her," Clarken said.

Last preparation Bella Vella won three races from as many starts, kicking off with a win over 955 metres at Moonee Valley where she recorded 54.84 seconds, which was the fastest time for that distance last season.

She then won at Listed level at Morphettville Parks before claiming her win at Group One level in the Robert Sangster Stakes.