Debut winner Microphone will need to overcome the outside barrier draw if he is to remain unbeaten in the Listed Blue Diamond Preview for colts and geldings at Caulfield.

The Godolphin-owned colt has barrier 13 for Saturday's 1000m race which is one of two Blue Diamond Previews on the program along with the Group Three fillies Preview.

Microphone won narrowly over filly Pretty Brazen on debut in a straight-track race for juveniles at Flemington last Saturday week and he is the only horse among Saturday's field of colts and geldings to have won a race.

He was an early $4 favourite on Wednesday ahead of the Anthony Freedman-trained I Am Immortal who had tightened from $6 to $4.80 in early betting.

I Am Immortal, one of eight debutants in the field, won a recent Pakenham barrier trial in which the Phillip Stokes-trained Brazen Brando was third.

Stokes has entered Brazen Brando for Saturday's Preview with the colt set to jump from one gate inside Microphone in barrier 12 having had two barrier trials this preparation to ready him for a debut test.

He was a close second in a 1000m Morphettville trial early this month before his third in a 900m heat at Pakenham on January 15 behind I Am Immortal.

"It's a tough race," Stokes said.

"Brazen Brando has had two trials (this preparation) and I thought his first one was better than his second trial.

"In saying that it was the quickest trial of the morning and we probably rode him a bit too close. I think ridden a bit quieter he could show a better turn of foot.

"He worked well on Tuesday morning. I like the horse but I'd say he would be an each-way chance."

The fillies Preview (1000m) has a capacity field of 16 plus two emergencies with the Peter and Paul Snowden training partnership to have a strong hand with Gimcrack Stakes winner Catch Me the early favourite ahead of her Victory Vein Plate-winning stablemate Anaheed.

Catch Me, to be ridden by Kerrin McEvoy, has drawn wide in barrier 14 while Anaheed has barrier two.