Trainer Gai Waterhouse has brushed aside any concerns high-class mare More Joyous might have come to the end of her spring campaign, declaring her certain to go on to the Cox Plate and probably the Mackinnon Stakes at Flemington on Derby Day a week later.

More Joyous finished a game, but slightly disappointing fourth when favourite behind Solzhenitsyn in the Toorak Handicap at Caulfield last weekend after doing more work than any other runner and carrying 60kg.

The effort prompted fears she may be again displaying her tendency to rapidly lose condition and form after a few runs.

Quite the opposite, according to Waterhouse.

"I think she needed Saturday's run," Waterhouse said.

"She looks a picture ... she'll run in the Cox Plate, and run very well.

"Then I'd back her up in the Mackinnon and then go to the paddock."

More Joyous has never had more than five runs in a preparation and has generally only produced three or four high-quality efforts each campaign.

The Cox Plate will be her fourth run this time in.

Waterhouse gave the mare a relatively easy morning on Thursday in a gallop on the course proper at Moonee Valley where she acted as lead horse for another of her trainer's three Cox Plate runners, Proisir.

More Joyous led out by six lengths but was held together from the 400m at which point Craig Newitt on Proisir applied some pressure, easily running past the mare entering the straight.

The effort, Proisir's first at the Valley, pleasantly surprised his trainer.

"I thought he might have been a bit geeky," she said.

"He surprised me, he was very professional."

While Waterhouse's other three-year-old Cox Plate entrant Pierro has been a ready-made racehorse, Proisir has been a late developer and something of a revelation.

"He was a very effeminate horse when he came to me," she said.

"You wouldn't say that now.

"He's very masculine and very strong.

"He's been difficult to handle, a lot of maintenance, a challenge, but a really worthwhile one."

Newitt, who rides Proisir in the Cox Plate, tended to agree after riding the colt for the first time, comparing his optimism this year to that of 2006 when he finished third to Fields Of Omagh in a three-way photo on Pompeii Ruler.

"I went to the races that day thinking we would win," Newitt said.

"I'm going into the race this time as confident as I was with Pompeii Ruler, just on what he showed me today."