Luck deserted Vibrant Rouge at Caulfield last start but trainer Glenn Thornton is confident the mare can make up for that disappointment with victory at the same track on Saturday.

Vibrant Rouge was a luckless second two weeks ago, caught behind a wall of horses early in the straight before flashing home late to go down by a neck to Serene Star.

The four-year-old is favourite to turn the tables in Paul Williamson Handicap (1200m).

"I'm probably happier with her now than I was going into that race the other day," Thornton said.

"Of course you've got to have a bit of luck and it's just not with her at the moment. She's had three runs at Caulfield and not had much luck in any of them. Let's hope that changes tomorrow."

Vibrant Rouge is ridden by Thornton's son Damien, and the trainer believes both the horse and the apprentice rider were a victim of circumstances last start.

He said the speed wasn't nearly as quick as they anticipated and the field bunched up on the turn.

"Of course she was unlucky, but in all fairness there wasn't a lot anyone could do," the trainer said.

Damien Thornton sits second on the Melbourne apprentices' premiership with 22 wins, nine behind frontrunner Chad Schofield who has spent a significant portion of the season on the sidelines through suspensions.

Melbourne's leading jockey Glen Boss, meanwhile, will be out to build on his tally at Caulfield as he zeroes in on a first premiership.

He has a 17-win advantage over Craig Williams, who won't ride in Melbourne for the rest of the season, but more importantly for Boss, he is 19 ahead of reigning title-holder Luke Nolen who rides in Adelaide on Saturday.

Boss rides the favourite Great De Here in the opening race for two-year-olds and has other strong chances including Midsummer Sun for trainer Sam Kavanagh.

Midsummer Sun was a first-up winner in Australia at Morphettville and Kavanagh has elected to go run him in the Peter Street Handicap over 2000m at Caulfield instead of Saturday's R A Lee Stakes (1600m) in Adelaide.