Aegon has done his part by recovering from his defeat, trialling nicely under raceday rider Kerrin McEvoy last week and working brilliantly on Tuesday.
So Forsman is confident he has made the right tactical choice and his 2000 Guineas winner is ready to take on the older horses but the Doncaster is not looking quite as attractive as it was a month ago.
Back then Aegon looked thrown in with 52.5kg, which became 53kg at withdrawal time, but since then other class three-year-olds such as Mo'unga have joined the Doncaster party and carry just 49.5kg.
So Aegon finds himself in the top half of the weights and only getting 3kg off All-Star Mile winner Mugatoo.
"At the time we decided on the Doncaster him getting in carrying 52.5kg sounded great but a few others have come in on even lighter weights and he is not that well weighted anymore."
Also trending in the wrong direction is the Randwick track which was a heavy9 last night after rain on Wednesday night.
"I wanted give in the track and a slow7 would be great so I am hoping it gets back to that," Forsman said.
"But heavy would be another challenge all together and that could suit an older horse like Mugatoo."
Forsman knows he can't control those factors, though, and he has a fit, happy horse with a decent draw trying to do what his own sire Sacred Falls did: win the Doncaster on a wet track as a three-year-old, something Sacred Falls repeated the next season at four.
"I think he can still win it but he needs nothing to go wrong," explains Forsman.
"If the track gets back to soft and he gets the right sort of run then he can win but if he gets leaned all over in a big field, he may not know how to handle it.
"So it won't be easy."
The same applies to stablemate The Frontman in Saturday's A$2 million ATC Derby, although the wetter track probably aids him more.
He was outpaced on a good track in the Tulloch last week but he proved he can handle a slugging wet 2400m when third to Rocket Spade in the New Zealand Derby at Ellerslie last month.
"I don't think it will bother him and I am willing to forgive him for last week.
"He is well and happy in himself but it is a good field and the two who beat him home at Ellerslie [Milford being the other] are in there.
"We are sure he will stay though which is half the battle in the derbies."
The stable also has Quick Thinker in the Chairman's Handicap and after winning the ATC Derby last year on a heavy track he looks well-suited albeit with moderate form.