Stewart said that tractability is one reason Minaj has made the trip home across the Tasman for the Million.
"She has the right attitude, which is a huge help," he told the Herald.
"Right from her first jump out we knew she had the ability to bring over here so it has always been the aim.
"But she wouldn't be here is she wasn't good enough and she is a natural runner, as you saw today."
Stewart said the hard Flemington track may have been behind Minaj's last-start fourth in a good form race but while Ellerslie has been baking in the Auckland heat, the track won't be a concern on Sunday.
"That track is perfect; she loved it."
Minaj was an impressive winner on her debut at Mornington and has settled in perfectly at Shaune Ritchie's stables. "Shaune and his team and Butch Castles from the club here have made the trip a lot easier for us, which is a huge help when you are chasing a $1 million race.
"But she is right where she needs to be at the moment."
The draw for the Karaka Million will be made today, with the TAB market expected tonight.