Bush youngster Rocket Tiger has upstaged his more fancied city rivals to give trainer Scott Spackman a Boxing Day milestone at Randwick.

Ridden by Kathy O'Hara, the home-bred was the Wagga Wagga trainer's first Sydney metropolitan winner and an emotional Spackman said it was a special moment.

"I'm just so proud of this little horse. This is my first city winner. I'm just rapt," Spackman said.

"I said to Kath before the race, he is the type of horse who, if he gets his head in front, he doesn't like anything going past him and he's done it today."

"He is the best horse I've had ever."

A winner on debut at Canberra, Rocket Tiger sat outside the leader and race favourite Vandoula Lass but she was unable to match him when he laid down the gauntlet.

Rocket Tiger ($26) scored by a long head over Vandoula Lass ($2.70 fav) with Vianello ($4.20) making ground another short neck away.

TAB fixed odds immediately eased Vandoula Lass from $9 to $13 for next month's Magic Millions Classic at the Gold Coast as Spackman dared to dream with Rocket Tiger.

"He will go for a quick little break now and I'll speak to the owner, but we've probably got a Black Opal or a Wellington Boot (in mind)," Spackman said.

"But God, they're talking a Slipper chance here too and we've knocked them off so I don't know. The world is his oyster."

O'Hara said Rocket Tiger dug deep when she asked him for a supreme effort over the final stages of Saturday's race.

"He was super tough and he put his head down when it counted. He wanted to win," O'Hara said.

"He was good last start, he was even better here today and he's got a lot of improvement in him."

Silver Thorn was a late scratching after becoming fractious in the barriers and causing jockey James McDonald to jam his knee against the stalls.

McDonald emerged limping but toughed it out to continue riding and booted home the next winner, Pinnacle Prince, in the Highway Handicap.

"It actually feels more comfortable out on a horse than it does walking. I just got it caught up there and it might be a bit worse tomorrow," McDonald said.