Clinton McDonald believes Diamond Effort is up to the challenge of keeping her undefeated record this year intact when she steps up to Group One company in the Moir Stakes.

Her task will be made easier by the absence of in-form three-year-old Anders, who has an elevated temperature and won't run.

McDonald realises Diamond Effort is facing her biggest challenge at Moonee Valley as she bids to make it six straight wins in 2020.

She will be up against sprinters the calibre of flying Perth mare Fabergino, Golden Slipper placegetter Away Game, Bella Vella and Hanseatic in the 1000 metre event.

McDonald is approaching the Moir with a degree of confidence, saying Diamond Effort will have a couple of key advantages over her rivals.

Firstly, McDonald is excited about the wet weather predicted towards the end of the week in Melbourne.

Secondly, he said Diamond Effort has learnt to settle in her races which should gain her a perfect position off the speed in what shapes as a fast-run race.

"She's going great. She gets her opportunity to step up in grade and she deserves a crack at it," McDonald said.

"Her wins have all been great. Her last-start win at Caulfield was against the pattern as she was off the speed.

"She pinned her ears back and got home. Also, it was a good track and she's better suited on a wet track.

"There's going to be so much speed with the likes of Pippie, Fabergino and Ashlor which will play into our hands.

"She's improved since her first-up win. She can handle pressure. She's a big, strong mare. There's going to be a lot in our favour."

McDonald said if Diamond Effort ran well she would have her next start in the Manikato Stakes at Moonee Valley, a month later on October 23.

Diamond Effort's winning streak began in February at Caulfield and she has since won at Flemington, Mornington and twice more at Caulfield, her latest victory on August 29 in the Group Three The Heath.

Ben Melham has ridden her in four of her past five wins and will be aboard again on Friday.