"Trent was really happy with his work," Baertschiger said.
"He worked with Silent Achiever. He looked to go better than her and ran the second-fastest last 400m of the morning."
Nash Rawiller rides Atmosphere today, but a jockey is yet to be confirmed for the Derby.
Baertschiger revealed he had received a few offers to buy a stake in Atmosphere but had refused them.
"I've had a few offers for 10 per cent of the horse but have knocked them back," Baertschiger said. "If someone wants to give me a million for him then they can have him."
Baertschiger said Atmosphere would spell after the Derby and be prepared for the autumn.
Murray Baker and Andrew Forsman are following a familiar three-year-old path with Eye Raced Ninety.
The Cambridge trainers have sent the son of Savabeel south for today's Listed Armadillo Stakes at Riccarton off the back of a last-start success closer to home.
"It's the same race Atlante won last year after he won the same maiden at Avondale," Baker said. "We think this horse has got a lot of ability and he's still in the 2000 Guineas."
To be ridden by Matthew Cameron, Eye Raced Ninety had placed at his two previous appearances before his breakthrough victory.
"I thought he won very well at Avondale and he's a big, strong horse and a full-brother to Warren The Rooster, who won the Wanganui Guineas," Baker said.
- AAP, NZ Racing Desk