Chris Waller believes both of his gallopers in the Cox Plate, Kolding and Humidor, will have to produce peak performances to be winning chances in the Moonee Valley showpiece.

Waller is aiming for his fifth victory in the Cox Plate having trained the incomparable Winx to win four in a row between 2015 and 2018 and he has assessed this year's race as being very open.

In a twist, Waller has rejuvenated the career of Humidor, who when trained by Darren Weir finished second to Winx in 2017 and third behind her the following year.

Humidor is the only horse to have challenged Winx in a Cox Plate as Hugh Bowman had to push her out to defeat him in 2017.

When Weir was disqualified, Humidor was transferred to two subsequent stables and lost form before finding his way to Waller.

He has flourished under the champion trainer, who produced the eight-year-old to win the Feehan Stakes first-up at his debut for the yard.

Humidor then continued his good form with a second in the Underwood Stakes and a third in the Caulfield Stakes.

As he hasn't been able to travel to Melbourne due to COVID-19 restrictions, Waller has gleaned a lot from jockey Craig Williams' assessments of how Humidor is progressing.

"I commend riders like Craig Williams in bringing the experience of racing closer to the public and the owners, as well as myself," Waller said.

"He has provided us with regular videos and he even sent vision on Tuesday of Humidor's gallop at Moonee Valley.

"It was a great insight for myself and the owners to see what Craig was going through in the middle of an important piece of work."

Waller said stablemate Kolding's last two wins indicated he was back to his best form and the trainer's confidence was boosted by the horse's victory over 2000 metres last start.

Kolding failed in two runs at Caulfield in the autumn but Waller said he appeared to be handling the Valley circuit.

"He is coping better with the bends at Moonee Valley compared to Caulfield but obviously we need to see this under race pressure when racing left-handed," Waller said.