Classic Unicorn couldn’t have been more impressive in his debut win but trainer Chris So Wai-yin is wary of his former boss as he looks to go back-to-back on Sunday in the Class Three Members Cup (1,000m) at Sha Tin.

The raw three-year-old was far too good for his rivals on June 2, leading all the way under the guidance of Zac Purton and now jumps up in grade after earning an 11-point ratings boost.

Classic Unicorn did plenty wrong in his first start, but the ability is clearly there for all to see and he should progress through the grades as he develops.

But when assessing the race, one rival in particular stood out to So – Seven Heavens – who is trained by his former mentor Caspar Fownes and will be ridden by Purton.

“I worry about my former boss’ horse Seven Heavens. He’s a good horse dropping back in class. I think he’s the one to beat,” So said.

“I’m confident with my horse, he’s still young and his last win was impressive, so fingers crossed he can get the job done. He trialled nicely and we’ve got a good draw.”

Given Classic Unicorn is a galloper on the up, you’d think it would be easy to secure a jockey, but it has been quite the opposite for his trainer on this occasion.

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Purton was the incumbent, but cannot ride at 116 pounds, so John Size’s stable jockey Joao Moreira put his hand up but he had to renege when his yard entered Gamechangers.

So managed to navigate the game of musical chairs by securing the services of Derek Leung Ka-chun, who galloped the horse on Thursday morning.

“It was lucky I could get Derek,” So said.

“Zac isn’t able to get the weight, so it wasn’t an option for him.

“Joao was supposed to ride him, but he called when the entries came out and said he could not because John Size’s plans had changed and he entered one.”

Seven Heavens does look to be one of his main rivals, returning to the Sha Tin straight for the first time since being a certainty beaten (he was the victim of interference) in March.

Tony Cruz’s Multimillion has won four races at the course and distance this season and will appreciate the weight relief Alfred Chan Ka-hei’s 10-pound claim will provide.

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The Dennis Yip Chor-hong-trained Goko is knocking on the door with back-to-back placings, Highland Fortune is looking to bounce back from a disappointing performance while the wild card could be Lone Eagle, who looked good winning a recent trial and is having his first start for Ricky Yiu Poon-fai.

Classic Unicorn also performed well when untested in a trial last week and So is confident he will make his presence felt.

“He knows how to run, so I told the jockey just to let him sit handy in the trial and make sure he’s feeling well. If he put him under a bit of pressure he would’ve won. So far everything is positive,” So said.

“He will probably be the favourite and then let’s see – I’m hungry for winners.”