But Eustace is also not discounting the chances of filly High Emocean who will clash with her stablemate in Saturday's Mark Needham Handicap (2394m) at Caulfield in which she will be carrying 8kg less than Persan.
Persan has won four of his past five starts, including his past three in a row at Flemington, while High Emocean heads to Saturday's race for three-year-olds off wins in benchmark races at Echuca over 2100m in June and Sandown over 2400m last month at her past two starts.
After back-to-back wins over 2000m during June at Flemington, Persan continued his rise with a dominant win in the Banjo Paterson Series Final (2500m) for three-year-olds on July 4 at his most recent start.
The promising Persan, who rises from 59.5kg last start to 62kg, was the $3 favourite for Saturday's race on Friday just ahead of the Danny O'Brien-trained last-start winner Grinzinger Allee while High Emocean was on the fourth line of betting on race eve in a field which has been reduced to 11 after two scratchings.
Eustace believes Persan is the one to beat again but thinks High Emocean is also above average and will run well.
"I think Persan will be fine carrying the weight," Eustace, who trains in partnership with Ciaron Maher, said.
"He's in really good order and has trained on beautifully. The three weeks between runs with the busy schedule is ideal for him.
"And High Emocean I think will actually give him a run for his money. She's getting eight kilos off him and a bit of time between runs definitely suits her.
"I think she will run very well too."
Persan is likely to be given a freshen up after Saturday ahead of a spring staying campaign.
"I think he's a horse who's just in a nice rhythm now," Eustace said.
"Mentally he's there and I think that's been the main thing with him, just getting him right mentally because he was a bit highly strung.
"He's now a beautifully relaxed horse."