Craig Williams was quick to find out why unbeaten filly Assail is at the top of the Magic Millions Classic market when he partnered her in an exhibition gallop at Warwick Farm on Saturday.

Williams picked up the ride on Assail for the $2 million Magic Millions next Saturday after jockey Peter Robl was suspended.

Williams made the trip from Melbourne to Sydney just to ride the Clarry Conners-trained filly in a gallop between races at Warwick Farm.

He left suitably impressed.

"I was really happy with that," Williams said.

"I've watched her replays and she's either favourite or second favourite for the Magic Millions and the way she just worked I can see why.

"She's got a very smart head on her shoulders. Clarry knows what he's doing with this filly and for these races and it was great getting a feel of her today."

Assail is equal favourite at $3 for the Magic Millions along with Melbourne colt Clevadude.

She sat a couple of lengths off older stablemate The Last General in her working gallop from the 600m mark before joining him on the home turn.

Assail swept straight past her mate in the straight to win the gallop by almost two lengths.

The time for the 600m was 33.8 seconds.