Victoria Derby favourite It's A Dundeel has firmed again with the market reshuffled following the withdrawal of Geelong Classic winner Solemn.

Sheikh Mohammed's colt developed a temperature on Monday night and trainer Peter Snowden pulled him out of Saturday's blue riband.

He was at $6 with the TAB which has brought It's A Dundeel back into $2.50 after he eased from $1.90 to $2.80 following his second in the Vase at Moonee Valley.

His conqueror Super Cool is on a crowded second line at $6.50 alongside Norman Robinson Stakes first and second Hvasston and Honorius.

Fiveandahalfstar, who ignited Derby hopes for trainer Anthony Cummings with a win at Rosehill on Saturday and had been the subject of support, is now likely to tackle an easier race during the Flemington carnival.

While acknowledging It's A Dundeel as the one to beat, trainer David Payne believes Honorius is peaking at the right time.

Part of Payne's confidence comes from the colt's two wins over 1550m and 1800m as a two-year-old.

The former South African supported the concept in numbers and said the grounding was necessary if you wanted to run a young three-year-old over the 2500 metres of Saturday's Derby.

"These horses are bred to stay," Payne said.

"They run two-year-olds over longer distances in other parts of the world.

"We used to do it in South Africa and I think it's a good thing."

Honorius is by Holy Roman Emperor from unraced mare Zarinia and is a half-brother to South African champion Igugu.

Zarinia's family produced French champion Zarkava who counts the Prix de l'Arc de Triomphe as her greatest win.

Honorius has finished behind It's A Dundeel twice in Sydney when second in the Group Three Gloaming (1800m) and third in the Group One Spring Champion Stakes (2000m).

Despite It's A Dundeel's defeat in the Vase, Payne is among those who believe the market has it right.

"He will be much better on the bigger track at Flemington," he said.

"But I'm pretty happy with my horse."

The field for the Derby will be finalised on Wednesday with a capacity field of 16 expected.