Zac Purton remains “hopeful” of partnering Exultant in Sunday’s Group One Champions & Chater Cup after succumbing to back spasms at Happy Valley on Wednesday night, while his rival Joao Moreira put on a clinic with a five-timer in his absence.

The Australian felt his back go as he drove Red Majesty to victory on the opening race, forcing him to stand down from his remaining seven rides.

It places him in some doubt for the final Group One meeting of the Hong Kong season where Exultant is shooting for a hat-trick of wins in the 2,400m feature.

“I’m hopeful of being able to ride on Sunday. The doctors have been good, they’ve given me the right medication and hopefully that helps. If it works then hopefully I’m there on Sunday,” Purton said.

“I’ve had this issue before. Nine or 10 years ago was the first time, four years ago was the last time before tonight.”

“It doesn’t happen regularly. We’re athletes, we’re sportsmen and from time to time it happens,” he continued.

“Normally it’s a time thing. Sometimes it can take three days to relax, sometimes it can take 10 days. I’ll know more when I wake up in the morning.”

The four-time champion can pinpoint the moment when it happened.

“My horse began awkwardly out of the gate and that pulled me at that point in time and it just progressively got worse,” Purton said.

“My lower back went into spasm and all the lower muscles reacted accordingly. The doctors did all they could. I had the second race off and it’s just not well enough to be able to continue riding tonight.”

To add insult to injury, Purton’s nemesis Moreira extended his lead in the championship with a dominant display and if the fat lady is not singing just yet, she’s warming up her vocal cords.

With 15 meetings remaining, the Magic Man holds a 128-110 advantage after saluting on Nitro Express, Universal Go Go, Rhapsody, Savvy Kingman and Transcendent.

It matched his previous best at the unique city circuit, which came on October 12, 2016.

“It’s not often we get these days and no doubt I’m very happy with that,” Moreira said.

“Riding five winners tonight is very meaningful, I’m very thankful for all the support that everybody gives me and that fires me up – it gives me even more confidence.

“Savvy Kingman was the most satisfying winner for me because his last two starts I didn’t give him the best rides, I was a bit unlucky.

“I had a challenge for myself to give him a better ride and now that I know him a little bit better I was able to get the best out of him.”

The David Ferraris-trained Nitro Express broke a 1,575-day drought when he led all the way in the first section of the Class Five Tan Shan River Handicap (1,650m), collecting his fourth victory from 62 starts and first since January 2017. It was the first of a double for the South African handler, who also won with Xiang Bai Qi.

After Nitro Express, Moreira followed up with Universal Go Go for Francis Lui Kin-wai, the John Size-trained Rhapsody and Frankie Lor Fu-chuen’s Savvy Kingman before putting the cherry on top with Transcendent, from the Tony Cruz stable.

Speaking of extending leads in the premiership, Size did just that as he pocketed a double with Rhapsody and Ping Hai Galaxy (Antoine Hamelin).

The 11-time champion now has 62 wins for the campaign, three ahead of Caspar Fownes and six more than Danny Shum Chap-shing.