Zac Spain's infatuation with tough galloper Streets Of Avalon has gone to another level as the tough on-pacer provided the 24-year-old with his first Group One win when successful in the Orr Stakes.

Spain described his association with Streets Of Avalon as a career changer.

He said he could barely contain his excitement when Streets Of Avalon fought off a determined challenge from Imaging to win the 1400 metre Group One at Caulfield.

"I celebrated a bit after the line and was calling out a fair bit," Spain said.

"He's just been a super horse to me. He was my first Listed winner, then Group Two and now a Group One."

Spain said riding in Melbourne was competitive and difficult so he had to make the most of his opportunities.

"I don't ride in town much but when you ride these good horses in town you need to capitalise and to get the job done is fantastic," he said.

Streets Of Avalon's trainer Shane Nichols said the galloper's managing owner Phil Warren was happy to stick with Spain and he had grasped his opportunity.

"He's done a good job with him, Zac. I think he's (won) six on him now and his first Group One," Nichols said.

"They just need the opportunity and they need to seize them when they get it. He seized it and he got it. Well done."

Nichols expressed his admiration for his six year-old, who has now won 10 races from 54 starts and $1.7 million in stakes.

"He's a warrior. For a horse that has had as many runs as he's had to still be fronting up winning Group Ones is a remarkable performance," he said.

Five months ago Nichols suffered a serious heart attack and said he gave that muscle a good test in the closing stages.

"The heart was racing. I gave it a test out and it came through with flying colours. I was pretty emotional after the Australia Stakes and now I'm just pumped," he said.

Streets Of Avalon ($8.50) defeated Sydneysider Imaging ($6.50) by a half-length with Crosshaven ($3.10) another 2-1/4 lengths away third.

The flop of the race was the $2.70 favourite Sir Dragonet who was never a factor and finished seventh, beaten 10 lengths.

His jockey Glen Boss said Sir Dragonet felt very dour.

"We've learned a valuable lesson today as he's obviously going to be better on soft (ground) but I'm not going to blame the track at all," Boss said.

"The track is in great condition and his action was fine. We just found that he hasn't got the speed to win over seven (furlongs)."